| Message ID | 20240126184639.8187-2-mario.limonciello@amd.com |
|---|---|
| State | New |
| Headers | show |
| Series | Fetch EDID from ACPI _DDC method if available | expand |
On Fri, Jan 26, 2024 at 7:55 PM Mario Limonciello <mario.limonciello@amd.com> wrote: > > The ACPI specification allows for an EDID to be up to 512 bytes but > the _DDC EDID fetching code will only try up to 256 bytes. > > Modify the code to instead start at 512 bytes and work it's way > down instead. > > Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/Apx_B_Video_Extensions/output-device-specific-methods.html#ddc-return-the-edid-for-this-device > Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> > --- > drivers/acpi/acpi_video.c | 23 ++++++++++++++++------- > 1 file changed, 16 insertions(+), 7 deletions(-) > > diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c > index 62f4364e4460..b3b15dd4755d 100644 > --- a/drivers/acpi/acpi_video.c > +++ b/drivers/acpi/acpi_video.c > @@ -624,6 +624,10 @@ acpi_video_device_EDID(struct acpi_video_device *device, > arg0.integer.value = 1; > else if (length == 256) > arg0.integer.value = 2; > + else if (length == 384) > + arg0.integer.value = 3; > + else if (length == 512) > + arg0.integer.value = 4; It looks like switch () would be somewhat better. Or maybe even arg0.integer.value = length / 128; The validation could be added too: if (arg0.integer.value > 4 || arg0.integer.value * 128 != length) return -EINVAL; but it is pointless, because the caller is never passing an invalid number to it AFAICS. > else > return -EINVAL; > > @@ -1443,7 +1447,7 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, > > for (i = 0; i < video->attached_count; i++) { > video_device = video->attached_array[i].bind_info; > - length = 256; > + length = 512; > > if (!video_device) > continue; > @@ -1478,13 +1482,18 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, > > if (ACPI_FAILURE(status) || !buffer || > buffer->type != ACPI_TYPE_BUFFER) { > - length = 128; > - status = acpi_video_device_EDID(video_device, &buffer, > - length); > - if (ACPI_FAILURE(status) || !buffer || > - buffer->type != ACPI_TYPE_BUFFER) { > - continue; > + while (length) { I would prefer a do {} while () loop here, which could include the first invocation of acpi_video_device_EDID() too (and reduce code duplication a bit). > + length -= 128; > + status = acpi_video_device_EDID(video_device, &buffer, > + length); No line break, please. > + if (ACPI_FAILURE(status) || !buffer || > + buffer->type != ACPI_TYPE_BUFFER) { > + continue; > + } > + break; > } > + if (!length) > + continue; > } > > *edid = buffer->buffer.pointer; > --
On 1/29/2024 07:54, Rafael J. Wysocki wrote: > On Fri, Jan 26, 2024 at 7:55 PM Mario Limonciello > <mario.limonciello@amd.com> wrote: >> >> The ACPI specification allows for an EDID to be up to 512 bytes but >> the _DDC EDID fetching code will only try up to 256 bytes. >> >> Modify the code to instead start at 512 bytes and work it's way >> down instead. >> >> Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/Apx_B_Video_Extensions/output-device-specific-methods.html#ddc-return-the-edid-for-this-device >> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> >> --- >> drivers/acpi/acpi_video.c | 23 ++++++++++++++++------- >> 1 file changed, 16 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c >> index 62f4364e4460..b3b15dd4755d 100644 >> --- a/drivers/acpi/acpi_video.c >> +++ b/drivers/acpi/acpi_video.c >> @@ -624,6 +624,10 @@ acpi_video_device_EDID(struct acpi_video_device *device, >> arg0.integer.value = 1; >> else if (length == 256) >> arg0.integer.value = 2; >> + else if (length == 384) >> + arg0.integer.value = 3; >> + else if (length == 512) >> + arg0.integer.value = 4; > > It looks like switch () would be somewhat better. > > Or maybe even > > arg0.integer.value = length / 128; > > The validation could be added too: > > if (arg0.integer.value > 4 || arg0.integer.value * 128 != length) > return -EINVAL; > > but it is pointless, because the caller is never passing an invalid > number to it AFAICS. > Thanks. I'll swap over to one of these suggestions. I will also split this patch separately from the other as the other will take some time with refactoring necessary in DRM that will take a cycle or two. >> else >> return -EINVAL; >> >> @@ -1443,7 +1447,7 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, >> >> for (i = 0; i < video->attached_count; i++) { >> video_device = video->attached_array[i].bind_info; >> - length = 256; >> + length = 512; >> >> if (!video_device) >> continue; >> @@ -1478,13 +1482,18 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, >> >> if (ACPI_FAILURE(status) || !buffer || >> buffer->type != ACPI_TYPE_BUFFER) { >> - length = 128; >> - status = acpi_video_device_EDID(video_device, &buffer, >> - length); >> - if (ACPI_FAILURE(status) || !buffer || >> - buffer->type != ACPI_TYPE_BUFFER) { >> - continue; >> + while (length) { > > I would prefer a do {} while () loop here, which could include the > first invocation of acpi_video_device_EDID() too (and reduce code > duplication a bit). > >> + length -= 128; >> + status = acpi_video_device_EDID(video_device, &buffer, >> + length); > > No line break, please. > >> + if (ACPI_FAILURE(status) || !buffer || >> + buffer->type != ACPI_TYPE_BUFFER) { >> + continue; >> + } >> + break; >> } >> + if (!length) >> + continue; >> } >> >> *edid = buffer->buffer.pointer; >> --
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c index 62f4364e4460..b3b15dd4755d 100644 --- a/drivers/acpi/acpi_video.c +++ b/drivers/acpi/acpi_video.c @@ -624,6 +624,10 @@ acpi_video_device_EDID(struct acpi_video_device *device, arg0.integer.value = 1; else if (length == 256) arg0.integer.value = 2; + else if (length == 384) + arg0.integer.value = 3; + else if (length == 512) + arg0.integer.value = 4; else return -EINVAL; @@ -1443,7 +1447,7 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, for (i = 0; i < video->attached_count; i++) { video_device = video->attached_array[i].bind_info; - length = 256; + length = 512; if (!video_device) continue; @@ -1478,13 +1482,18 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, if (ACPI_FAILURE(status) || !buffer || buffer->type != ACPI_TYPE_BUFFER) { - length = 128; - status = acpi_video_device_EDID(video_device, &buffer, - length); - if (ACPI_FAILURE(status) || !buffer || - buffer->type != ACPI_TYPE_BUFFER) { - continue; + while (length) { + length -= 128; + status = acpi_video_device_EDID(video_device, &buffer, + length); + if (ACPI_FAILURE(status) || !buffer || + buffer->type != ACPI_TYPE_BUFFER) { + continue; + } + break; } + if (!length) + continue; } *edid = buffer->buffer.pointer;
The ACPI specification allows for an EDID to be up to 512 bytes but the _DDC EDID fetching code will only try up to 256 bytes. Modify the code to instead start at 512 bytes and work it's way down instead. Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/Apx_B_Video_Extensions/output-device-specific-methods.html#ddc-return-the-edid-for-this-device Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> --- drivers/acpi/acpi_video.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-)