From patchwork Thu Jun 9 15:47:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ivan Bornyakov X-Patchwork-Id: 580916 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6FABC433EF for ; Thu, 9 Jun 2022 16:10:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241723AbiFIQK4 (ORCPT ); Thu, 9 Jun 2022 12:10:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238864AbiFIQKz (ORCPT ); Thu, 9 Jun 2022 12:10:55 -0400 Received: from mail.pr-group.ru (mail.pr-group.ru [178.18.215.3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 988741451C3; Thu, 9 Jun 2022 09:10:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=metrotek.ru; s=mail; h=from:subject:date:message-id:to:cc:mime-version:content-transfer-encoding: in-reply-to:references; bh=gxaS72L5sOWXmLEo7uXaBq1dWL9iA3Jtftp2VqgrAts=; b=GyExpkG5Snh8Tqz4274OqGlkJJw1eJs9sJORpnjWTYKggSMWdcVSJ6vuPgitt6fnSgvJnhYn7ux2e 0zj8g45tjSYdJuTNU/VD73AFyx6yZLX9LOVpTdyHcKPiGLgjUvfwCCMVQOxfm6YZssFOJkqx/gm1Zh JAx89CnVukTh++TqPrdItdu3hmGKWRMhwMNKqFx26PFef3UIfzihhd3/9UKcILMGQAWMx/lzFop8i8 gHV+tlSaXLDpVdhA/dy5aqJ+Ip/BFeBkKZZgC9Ey2wYNidGRrGgXF1S94lPWO6F1qtBJ1m7pvX/Xw3 MTRCujD6H90yV/p0wuoB6bqGhmPIRDw== X-Kerio-Anti-Spam: Build: [Engines: 2.16.3.1424, Stamp: 3], Multi: [Enabled, t: (0.000012,0.042503)], BW: [Enabled, t: (0.000017,0.000001)], RTDA: [Enabled, t: (0.073561), Hit: No, Details: v2.40.0; Id: 15.52k9p2.1g54jmjpq.30fo; mclb], total: 0(700) X-Footer: bWV0cm90ZWsucnU= Received: from localhost.localdomain ([178.70.36.174]) (authenticated user i.bornyakov@metrotek.ru) by mail.pr-group.ru with ESMTPSA (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256 bits)); Thu, 9 Jun 2022 19:10:29 +0300 From: Ivan Bornyakov To: mdf@kernel.org, hao.wu@intel.com, yilun.xu@intel.com, trix@redhat.com, corbet@lwn.net Cc: Ivan Bornyakov , Conor.Dooley@microchip.com, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, linux-fpga@vger.kernel.org, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, system@metrotek.ru, Ivan Bornyakov Subject: [PATCH v17 1/4] fpga: fpga-mgr: support bitstream offset in image buffer Date: Thu, 9 Jun 2022 18:47:49 +0300 Message-Id: <20220609154752.20781-2-i.bornyakov@metrotek.ru> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220609154752.20781-1-i.bornyakov@metrotek.ru> References: <20220609154752.20781-1-i.bornyakov@metrotek.ru> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org At the moment FPGA manager core loads to the device entire image provided to fpga_mgr_load(). But it is not always whole FPGA image buffer meant to be written to the device. In particular, .dat formatted image for Microchip MPF contains meta info in the header that is not meant to be written to the device. This is issue for those low level drivers that loads data to the device with write() fpga_manager_ops callback, since write() can be called in iterator over scatter-gather table, not only linear image buffer. On the other hand, write_sg() callback is provided with whole image in scatter-gather form and can decide itself which part should be sent to the device. Add header_size and data_size to the fpga_image_info struct and adjust fpga_mgr_write() callers with respect to them. * info->header_size indicates part at the beginning of image buffer that is *not* meant to be written to the device. It is optional and can be 0. * info->data_size is the size of actual bitstream data that *is* meant to be written to the device, starting at info->header_size from the beginning of image buffer. It is also optional and can be 0, which means bitstream data is up to the end of image buffer. Also add parse_header() callback to fpga_manager_ops, which purpose is to set info->header_size and info->data_size. At least initial_header_size bytes of image buffer will be passed into parse_header() first time. If it is not enough, parse_header() should set desired size into info->header_size and return -EAGAIN, then it will be called again with greater part of image buffer on the input. Signed-off-by: Ivan Bornyakov --- drivers/fpga/fpga-mgr.c | 243 +++++++++++++++++++++++++++++----- include/linux/fpga/fpga-mgr.h | 17 ++- 2 files changed, 229 insertions(+), 31 deletions(-) diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c index 08dc85fcd511..0854fbc8f11e 100644 --- a/drivers/fpga/fpga-mgr.c +++ b/drivers/fpga/fpga-mgr.c @@ -74,6 +74,15 @@ static inline int fpga_mgr_write_complete(struct fpga_manager *mgr, return 0; } +static inline int fpga_mgr_parse_header(struct fpga_manager *mgr, + struct fpga_image_info *info, + const char *buf, size_t count) +{ + if (mgr->mops->parse_header) + return mgr->mops->parse_header(mgr, info, buf, count); + return 0; +} + static inline int fpga_mgr_write_init(struct fpga_manager *mgr, struct fpga_image_info *info, const char *buf, size_t count) @@ -136,24 +145,145 @@ void fpga_image_info_free(struct fpga_image_info *info) EXPORT_SYMBOL_GPL(fpga_image_info_free); /* - * Call the low level driver's write_init function. This will do the + * Call the low level driver's parse_header function with entire FPGA image + * buffer on the input. This will set info->header_size and info->data_size. + */ +static int fpga_mgr_parse_header_mapped(struct fpga_manager *mgr, + struct fpga_image_info *info, + const char *buf, size_t count) +{ + int ret; + + mgr->state = FPGA_MGR_STATE_PARSE_HEADER; + ret = fpga_mgr_parse_header(mgr, info, buf, count); + + if (info->header_size + info->data_size > count) { + dev_err(&mgr->dev, "Bitsream data outruns FPGA image\n"); + ret = -EINVAL; + } + + if (ret) { + dev_err(&mgr->dev, "Error while parsing FPGA image header\n"); + mgr->state = FPGA_MGR_STATE_PARSE_HEADER_ERR; + } + + return ret; +} + +/* + * Call the low level driver's parse_header function with first fragment of + * scattered FPGA image on the input. If header fits first fragment, + * parse_header will set info->header_size and info->data_size. If it is not, + * parse_header will set desired size to info->header_size and -EAGAIN will be + * returned. + */ +static int fpga_mgr_parse_header_sg_first(struct fpga_manager *mgr, + struct fpga_image_info *info, + struct sg_table *sgt) +{ + size_t header_size = mgr->mops->initial_header_size; + struct sg_mapping_iter miter; + int ret; + + mgr->state = FPGA_MGR_STATE_PARSE_HEADER; + + sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG); + if (sg_miter_next(&miter) && + miter.length >= header_size) + ret = fpga_mgr_parse_header(mgr, info, miter.addr, miter.length); + else + ret = -EAGAIN; + sg_miter_stop(&miter); + + if (ret && ret != -EAGAIN) { + dev_err(&mgr->dev, "Error while parsing FPGA image header\n"); + mgr->state = FPGA_MGR_STATE_PARSE_HEADER_ERR; + } + + return ret; +} + +/* + * Copy scattered FPGA image fragments to temporary buffer and call the + * low level driver's parse_header function. This should be called after + * fpga_mgr_parse_header_sg_first() returned -EAGAIN. In case of success, + * pointer to the newly allocated image header copy will be set into *ret_buf + * and its size will be returned. *ret_buf needs to be freed by caller. + */ +static ssize_t fpga_mgr_parse_header_sg(struct fpga_manager *mgr, + struct fpga_image_info *info, + struct sg_table *sgt, char **ret_buf) +{ + size_t len, header_size = mgr->mops->initial_header_size; + char *buf = NULL; + int ret; + + do { + if (info->header_size) + header_size = info->header_size; + + buf = krealloc(buf, header_size, GFP_KERNEL); + if (!buf) { + ret = -ENOMEM; + break; + } + + len = sg_copy_to_buffer(sgt->sgl, sgt->nents, buf, header_size); + if (len != header_size) { + ret = -EFAULT; + break; + } + + ret = fpga_mgr_parse_header(mgr, info, buf, header_size); + if (ret == -EAGAIN && info->header_size <= header_size) { + dev_err(&mgr->dev, "Requested invalid header size\n"); + ret = -EFAULT; + } + } while (ret == -EAGAIN); + + if (ret) { + dev_err(&mgr->dev, "Error while parsing FPGA image header\n"); + mgr->state = FPGA_MGR_STATE_PARSE_HEADER_ERR; + kfree(buf); + buf = NULL; + } else { + ret = header_size; + } + + *ret_buf = buf; + + return ret; +} + +/* + * Call the low level driver's write_init function. This will do the * device-specific things to get the FPGA into the state where it is ready to - * receive an FPGA image. The low level driver only gets to see the first - * initial_header_size bytes in the buffer. + * receive an FPGA image. If info->header_size is defined, the low level + * driver gets to see at least first info->header_size bytes in the buffer, + * mgr->mops->initial_header_size otherwise. If neither initial_header_size + * nor header_size are not set, write_init will not get any bytes of image + * buffer. */ static int fpga_mgr_write_init_buf(struct fpga_manager *mgr, struct fpga_image_info *info, const char *buf, size_t count) { + size_t header_size; int ret; mgr->state = FPGA_MGR_STATE_WRITE_INIT; - if (!mgr->mops->initial_header_size) { + + if (info->header_size) + header_size = info->header_size; + else + header_size = mgr->mops->initial_header_size; + + if (header_size > count) + ret = -EINVAL; + else if (!header_size) ret = fpga_mgr_write_init(mgr, info, NULL, 0); - } else { - count = min(mgr->mops->initial_header_size, count); + else ret = fpga_mgr_write_init(mgr, info, buf, count); - } if (ret) { dev_err(&mgr->dev, "Error preparing FPGA for writing\n"); @@ -164,13 +294,13 @@ static int fpga_mgr_write_init_buf(struct fpga_manager *mgr, return 0; } -static int fpga_mgr_write_init_sg(struct fpga_manager *mgr, - struct fpga_image_info *info, - struct sg_table *sgt) +static int fpga_mgr_prepare_sg(struct fpga_manager *mgr, + struct fpga_image_info *info, + struct sg_table *sgt) { struct sg_mapping_iter miter; - size_t len; - char *buf; + ssize_t header_size; + char *header_buf; int ret; if (!mgr->mops->initial_header_size) @@ -180,26 +310,35 @@ static int fpga_mgr_write_init_sg(struct fpga_manager *mgr, * First try to use miter to map the first fragment to access the * header, this is the typical path. */ - sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG); - if (sg_miter_next(&miter) && - miter.length >= mgr->mops->initial_header_size) { - ret = fpga_mgr_write_init_buf(mgr, info, miter.addr, - miter.length); + ret = fpga_mgr_parse_header_sg_first(mgr, info, sgt); + /* If 0, header fits first fragment, call write_init on it */ + if (!ret) { + sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG); + if (sg_miter_next(&miter)) { + ret = fpga_mgr_write_init_buf(mgr, info, miter.addr, + miter.length); + sg_miter_stop(&miter); + return ret; + } sg_miter_stop(&miter); + /* + * If -EAGAIN, more sg buffer is needed, + * otherwise an error has occurred. + */ + } else if (ret != -EAGAIN) return ret; - } - sg_miter_stop(&miter); - /* Otherwise copy the fragments into temporary memory. */ - buf = kmalloc(mgr->mops->initial_header_size, GFP_KERNEL); - if (!buf) - return -ENOMEM; + /* + * Otherwise copy the fragments into temporary memory. + * Copying is done inside fpga_mgr_parse_header_sg() + */ + header_size = fpga_mgr_parse_header_sg(mgr, info, sgt, &header_buf); + if (header_size < 0) + return header_size; - len = sg_copy_to_buffer(sgt->sgl, sgt->nents, buf, - mgr->mops->initial_header_size); - ret = fpga_mgr_write_init_buf(mgr, info, buf, len); + ret = fpga_mgr_write_init_buf(mgr, info, header_buf, header_size); - kfree(buf); + kfree(header_buf); return ret; } @@ -227,7 +366,7 @@ static int fpga_mgr_buf_load_sg(struct fpga_manager *mgr, { int ret; - ret = fpga_mgr_write_init_sg(mgr, info, sgt); + ret = fpga_mgr_prepare_sg(mgr, info, sgt); if (ret) return ret; @@ -237,11 +376,40 @@ static int fpga_mgr_buf_load_sg(struct fpga_manager *mgr, ret = fpga_mgr_write_sg(mgr, sgt); } else { struct sg_mapping_iter miter; + size_t length, data_size; + bool last = false; + ssize_t count; + char *addr; + + data_size = info->data_size; + count = -info->header_size; sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG); while (sg_miter_next(&miter)) { - ret = fpga_mgr_write(mgr, miter.addr, miter.length); - if (ret) + count += miter.length; + + /* sg block contains only header, no data */ + if (count <= 0) + continue; + + if (count < miter.length) { + /* sg block contains both header and data */ + addr = miter.addr + miter.length - count; + length = count; + } else { + /* sg block contains pure data */ + addr = miter.addr; + length = miter.length; + } + + /* truncate last block to data_size, if needed */ + if (data_size && count > data_size) { + length -= count - data_size; + last = true; + } + + ret = fpga_mgr_write(mgr, addr, length); + if (ret || last) break; } sg_miter_stop(&miter); @@ -262,10 +430,21 @@ static int fpga_mgr_buf_load_mapped(struct fpga_manager *mgr, { int ret; + ret = fpga_mgr_parse_header_mapped(mgr, info, buf, count); + if (ret) + return ret; + ret = fpga_mgr_write_init_buf(mgr, info, buf, count); if (ret) return ret; + if (info->data_size) + count = info->data_size; + else + count -= info->header_size; + + buf += info->header_size; + /* * Write the FPGA image to the FPGA. */ @@ -424,6 +603,10 @@ static const char * const state_str[] = { [FPGA_MGR_STATE_FIRMWARE_REQ] = "firmware request", [FPGA_MGR_STATE_FIRMWARE_REQ_ERR] = "firmware request error", + /* Parse FPGA image header */ + [FPGA_MGR_STATE_PARSE_HEADER] = "parse header", + [FPGA_MGR_STATE_PARSE_HEADER_ERR] = "parse header error", + /* Preparing FPGA to receive image */ [FPGA_MGR_STATE_WRITE_INIT] = "write init", [FPGA_MGR_STATE_WRITE_INIT_ERR] = "write init error", diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h index 0f9468771bb9..cba8bb7827a5 100644 --- a/include/linux/fpga/fpga-mgr.h +++ b/include/linux/fpga/fpga-mgr.h @@ -22,6 +22,8 @@ struct sg_table; * @FPGA_MGR_STATE_RESET: FPGA in reset state * @FPGA_MGR_STATE_FIRMWARE_REQ: firmware request in progress * @FPGA_MGR_STATE_FIRMWARE_REQ_ERR: firmware request failed + * @FPGA_MGR_STATE_PARSE_HEADER: parse FPGA image header + * @FPGA_MGR_STATE_PARSE_HEADER_ERR: Error during PARSE_HEADER stage * @FPGA_MGR_STATE_WRITE_INIT: preparing FPGA for programming * @FPGA_MGR_STATE_WRITE_INIT_ERR: Error during WRITE_INIT stage * @FPGA_MGR_STATE_WRITE: writing image to FPGA @@ -42,6 +44,8 @@ enum fpga_mgr_states { FPGA_MGR_STATE_FIRMWARE_REQ_ERR, /* write sequence: init, write, complete */ + FPGA_MGR_STATE_PARSE_HEADER, + FPGA_MGR_STATE_PARSE_HEADER_ERR, FPGA_MGR_STATE_WRITE_INIT, FPGA_MGR_STATE_WRITE_INIT_ERR, FPGA_MGR_STATE_WRITE, @@ -85,6 +89,8 @@ enum fpga_mgr_states { * @sgt: scatter/gather table containing FPGA image * @buf: contiguous buffer containing FPGA image * @count: size of buf + * @header_size: offset in image buffer where bitstream data starts + * @data_size: size of bitstream. If 0, (count - header_size) will be used. * @region_id: id of target region * @dev: device that owns this * @overlay: Device Tree overlay @@ -98,6 +104,8 @@ struct fpga_image_info { struct sg_table *sgt; const char *buf; size_t count; + size_t header_size; + size_t data_size; int region_id; struct device *dev; #ifdef CONFIG_OF @@ -137,9 +145,13 @@ struct fpga_manager_info { /** * struct fpga_manager_ops - ops for low level fpga manager drivers - * @initial_header_size: Maximum number of bytes that should be passed into write_init + * @initial_header_size: minimum number of bytes that should be passed into + * parse_header and write_init. * @state: returns an enum value of the FPGA's state * @status: returns status of the FPGA, including reconfiguration error code + * @parse_header: parse FPGA image header to set info->header_size and + * info->data_size. In case the input buffer is not large enough, set + * required size to info->header_size and return -EAGAIN. * @write_init: prepare the FPGA to receive configuration data * @write: write count bytes of configuration data to the FPGA * @write_sg: write the scatter list of configuration data to the FPGA @@ -155,6 +167,9 @@ struct fpga_manager_ops { size_t initial_header_size; enum fpga_mgr_states (*state)(struct fpga_manager *mgr); u64 (*status)(struct fpga_manager *mgr); + int (*parse_header)(struct fpga_manager *mgr, + struct fpga_image_info *info, + const char *buf, size_t count); int (*write_init)(struct fpga_manager *mgr, struct fpga_image_info *info, const char *buf, size_t count); From patchwork Thu Jun 9 15:47:50 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ivan Bornyakov X-Patchwork-Id: 580915 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3FB1C43334 for ; Thu, 9 Jun 2022 16:11:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344165AbiFIQK7 (ORCPT ); Thu, 9 Jun 2022 12:10:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238243AbiFIQKz (ORCPT ); Thu, 9 Jun 2022 12:10:55 -0400 Received: from mail.pr-group.ru (mail.pr-group.ru [178.18.215.3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9892F3004D2; Thu, 9 Jun 2022 09:10:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=metrotek.ru; s=mail; h=from:subject:date:message-id:to:cc:mime-version:content-transfer-encoding: in-reply-to:references; bh=Rj/bc4NLOD6y0lx4o0+8nOenP1BSK87pxbF3KNpnDkc=; b=DvD4WUaARrJ7jB+MHzv+O6q7P8K0laOBe4EnuPcL1j5vrCh203QA3GL9vGq5JLZ6cJxAEQB6WtCc3 grLBr8z2+ipMLhUCrRCiF0s/6BbuUkRFHINHLgefpdqA8I7aRYokhuxgavEKCNTFZE6FiTTcm7kWtw w3iLKgRGJbXCyiWDP10uIY8qb8q6vdm675/yO7w23NVW3VofTVJu7KyNOUQ8z3gHresU9oVPeQV/wO d0S78+wIOi8xUOtJS33b4S6iUVaLZtzTYyfcsno8h7SgHhv3rUsyuPeCxazEpXdejXm0C7CY0Lfje/ b01IgiEZe3swehVgB0ILNrFBIQ6EyLg== X-Kerio-Anti-Spam: Build: [Engines: 2.16.3.1424, Stamp: 3], Multi: [Enabled, t: (0.000011,0.011574)], BW: [Enabled, t: (0.000021,0.000001)], RTDA: [Enabled, t: (0.137038), Hit: No, Details: v2.40.0; Id: 15.52k05u.1g54jmjqq.r1r; mclb], total: 0(700) X-Footer: bWV0cm90ZWsucnU= Received: from localhost.localdomain ([178.70.36.174]) (authenticated user i.bornyakov@metrotek.ru) by mail.pr-group.ru with ESMTPSA (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256 bits)); Thu, 9 Jun 2022 19:10:30 +0300 From: Ivan Bornyakov To: mdf@kernel.org, hao.wu@intel.com, yilun.xu@intel.com, trix@redhat.com, corbet@lwn.net Cc: Ivan Bornyakov , Conor.Dooley@microchip.com, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, linux-fpga@vger.kernel.org, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, system@metrotek.ru, Ivan Bornyakov Subject: [PATCH v17 2/4] docs: fpga: mgr: document parse_header() callback Date: Thu, 9 Jun 2022 18:47:50 +0300 Message-Id: <20220609154752.20781-3-i.bornyakov@metrotek.ru> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220609154752.20781-1-i.bornyakov@metrotek.ru> References: <20220609154752.20781-1-i.bornyakov@metrotek.ru> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Document newly introduced fpga_manager_ops callback parse_header() along with header_size and data_size fields of struct fpga_image_info. Signed-off-by: Ivan Bornyakov --- Documentation/driver-api/fpga/fpga-mgr.rst | 31 ++++++++++++++++------ 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/Documentation/driver-api/fpga/fpga-mgr.rst b/Documentation/driver-api/fpga/fpga-mgr.rst index 42c01f396dce..db0852bd3ddc 100644 --- a/Documentation/driver-api/fpga/fpga-mgr.rst +++ b/Documentation/driver-api/fpga/fpga-mgr.rst @@ -79,14 +79,29 @@ do the programming sequence for this particular FPGA. These ops return 0 for success or negative error codes otherwise. The programming sequence is:: - 1. .write_init - 2. .write or .write_sg (may be called once or multiple times) - 3. .write_complete - -The .write_init function will prepare the FPGA to receive the image data. The -buffer passed into .write_init will be at most .initial_header_size bytes long; -if the whole bitstream is not immediately available then the core code will -buffer up at least this much before starting. + 1. .parse_header + 2. .write_init + 3. .write or .write_sg (may be called once or multiple times) + 4. .write_complete + +The .parse_header function will set header_size and data_size to +struct fpga_image_info. If header_size is set, .write function will get image +buffer starting at header_size offset from the beginning. If data_size is set, +.write function will get data_size bytes of the image buffer, otherwise .write +will get data up to the end of image buffer. This will not affect .write_sg, +.write_sg will still get whole image in sg_table form. If FPGA image is a +single contiguous buffer, whole buffer will be passed into .parse_header. +If image is in scatter-gather form, core code will buffer up at least +.initial_header_size before the first call of .parse_header, if it is not +enough, .parse_header should set desired size into info->header_size and +return -EAGAIN, then it will be called again with greater part of image buffer +on the input. + +The .write_init function will prepare the FPGA to receive the image data. The +buffer passed into .write_init will be at least info->header_size bytes long, +if it's defined, otherwise .initial_header_size; if the whole bitstream is not +immediately available then the core code will buffer up at least this much +before starting. The .write function writes a buffer to the FPGA. The buffer may be contain the whole FPGA image or may be a smaller chunk of an FPGA image. In the latter