| Message ID | 20241203-const_dfc_done-v2-0-7436a98c497f@quicinc.com |
|---|---|
| Headers | show |
| Series | driver core: Constify API device_find_child() and adapt for various existing usages | expand |
On 2024/12/3 23:34, James Bottomley wrote: >>> This also enables an incremental migration. >> change the API prototype from: >> device_find_child(..., void *data_0, int (*match)(struct device *dev, >> void *data)); >> >> to: >> device_find_child(..., const void *data_0, int (*match)(struct device >> *dev, const void *data)); >> >> For @data_0, void * -> const void * is okay. >> but for @match, the problem is function pointer type incompatibility. >> >> there are two solutions base on discussions. >> >> 1) squashing likewise Greg mentioned. >> Do all of the "prep work" first, and then >> do the const change at the very end, all at once. >> >> 2) as changing platform_driver's remove() prototype. >> Commit: e70140ba0d2b ("Get rid of 'remove_new' relic from platform >> driver struct") >> >> introduce extra device_find_child_new() which is constified -> use >> *_new() replace ALL device_find_child() instances one by one -> >> remove device_find_child() -> rename *_new() to device_find_child() >> once. > Why bother with the last step, which churns the entire code base again? keep the good API name device_find_child(). > Why not call the new function device_find_child_const() and simply keep > it (it's descriptive of its function). That way you can have a patch > series without merging and at the end simply remove the old function. device_find_child is a good name for the API, 'find' already means const.
On 2024/12/5 00:42, James Bottomley wrote: >>>> introduce extra device_find_child_new() which is constified -> >>>> use *_new() replace ALL device_find_child() instances one by one >>>> -> remove device_find_child() -> rename *_new() to >>>> device_find_child() once. >>> Why bother with the last step, which churns the entire code base >>> again? >> keep the good API name device_find_child(). > Well, I think it's a good opportunity to rename the API better, but if > that's the goal, you can still do it with _Generic() without churning > the code base a second time. The example is in > slab.h:kmem_cache_create > i understand these solutions _Generic()/_new/squashing. every solutions have its advantages and disadvantages. i decide to use squashing solution for this concrete scenario after some considerations since: 1) it has the minimal patch count to achieve target. 2) every patch is valuable, but other solutions needs to undo beginning patch finally. 3) for the squashing patch, i will only make the least and simplest changes for various match functions, that will compensate its disadvantages. >>> Why not call the new function device_find_child_const() and simply >>> keep it (it's descriptive of its function). That way you can have >>> a patch series without merging and at the end simply remove the old >>> function. >> device_find_child is a good name for the API, 'find' already means >> const. > Not to me it doesn't, but that's actually not what I think is wrong > with the API name: it actually only returns the first match, so I'd > marginally prefer it to be called device_find_first_child() ... not > enough to churn the code to change it, but since you're doing that > anyway it might make sense as an update. name device_find_child appeared 18 years ago, it is good to keep this name developers known about. the API only return one device *, it should be obvious that it is the first device which meet matching condition. Other device finding APIs (bus|class|driver)_find_device() does not have concern about 'first' So, IMO, current name is good.
This patch series is to constify the following API: struct device *device_find_child(struct device *dev, void *data, int (*match)(struct device *dev, void *data)); To : struct device *device_find_child(struct device *dev, const void *data, device_match_t match); typedef int (*device_match_t)(struct device *dev, const void *data); Why to constify the API? - Protect caller's match data @*data which is for comparison and lookup and the API does not actually need to modify @*data. - Make the API's parameters (@match)() and @data have the same type as all of other device finding APIs (bus|class|driver)_find_device(). - All kinds of existing device matching functions can be directly taken as the API's argument, they were exported by driver core. How to constify the API? - Now, no (@match)() argument of the API usages is modifying its match data @*data after previous cleanup, so it is easy and safe to make its parameter @data take const void * as type. - Simplify involved codes further if it is possbile with benefits brought by constifying the API. Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com> --- Changes in v2: - Series v1 have no code review comments and are posted a long time ago, so may ignore differences. - Link to v1: https://lore.kernel.org/r/20240811-const_dfc_done-v1-0-9d85e3f943cb@quicinc.com - Motivation link: https://lore.kernel.org/lkml/917359cc-a421-41dd-93f4-d28937fe2325@icloud.com --- Zijun Hu (32): driver core: Constify API device_find_child() driver core: Introduce device_match_type() to match device with a device type drm/mediatek: Adapt for constified device_find_child() hwmon: Adapt for constified device_find_child() media: pci: mgb4: Adapt for constified device_find_child() thunderbolt: Adapt for constified device_find_child() gpio: sim: Remove gpio_sim_dev_match_fwnode() net: dsa: Adapt for constified device_find_child() pwm: Adapt for constified device_find_child() nvdimm: Adapt for constified device_find_child() libnvdimm: Simplify nd_namespace_store() implementation firewire: core: Adapt for constified device_find_child() serial: core: Adapt for constified device_find_child() usb: typec: class: Remove both cable_match() and partner_match() usb: typec: class: Adapt for constified device_find_child() slimbus: core: Simplify of_find_slim_device() implementation slimbus: core: Constify slim_eaddr_equal() slimbus: core: Adapt for constified device_find_child() scsi: iscsi: Constify API iscsi_find_flashnode_sess() scsi: qla4xxx: Adapt for constified iscsi_find_flashnode_sess() scsi: iscsi: Adapt for constified device_find_child() cxl/region: Adapt for constified device_find_child() cxl/pmem: Remove match_nvdimm_bridge() cxl/core/pci: Adapt for constified device_find_child() cxl/test: Adapt for constified device_find_child() sparc: vio: Adapt for constified device_find_child() bus: fsl-mc: Adapt for constified device_find_child() block: sunvdc: Adapt for constified device_find_child() firmware: arm_scmi: Adapt for constified device_find_child() efi: dev-path-parser: Adapt for constified device_find_child() rpmsg: core: Adapt for constified device_find_child() driver core: Simplify API device_find_child_by_name() implementation arch/sparc/kernel/vio.c | 6 +++--- drivers/base/core.c | 30 ++++++++++-------------------- drivers/block/sunvdc.c | 6 +++--- drivers/bus/fsl-mc/dprc-driver.c | 6 +++--- drivers/cxl/core/pci.c | 4 ++-- drivers/cxl/core/pmem.c | 9 +++------ drivers/cxl/core/region.c | 21 ++++++++++++--------- drivers/firewire/core-device.c | 4 ++-- drivers/firmware/arm_scmi/bus.c | 4 ++-- drivers/firmware/efi/dev-path-parser.c | 4 ++-- drivers/gpio/gpio-sim.c | 7 +------ drivers/gpu/drm/mediatek/mtk_drm_drv.c | 2 +- drivers/hwmon/hwmon.c | 2 +- drivers/media/pci/mgb4/mgb4_core.c | 4 ++-- drivers/nvdimm/bus.c | 2 +- drivers/nvdimm/claim.c | 9 +-------- drivers/pwm/core.c | 2 +- drivers/rpmsg/rpmsg_core.c | 4 ++-- drivers/scsi/qla4xxx/ql4_os.c | 3 ++- drivers/scsi/scsi_transport_iscsi.c | 10 +++++----- drivers/slimbus/core.c | 17 +++++------------ drivers/thunderbolt/retimer.c | 2 +- drivers/thunderbolt/xdomain.c | 2 +- drivers/tty/serial/serial_core.c | 4 ++-- drivers/usb/typec/class.c | 31 ++++++++++++++----------------- include/linux/device.h | 4 ++-- include/linux/device/bus.h | 1 + include/scsi/scsi_transport_iscsi.h | 4 ++-- net/dsa/dsa.c | 2 +- tools/testing/cxl/test/cxl.c | 2 +- 30 files changed, 89 insertions(+), 119 deletions(-) --- base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37 change-id: 20241201-const_dfc_done-aaec71e3bbea Best regards,