On Sun, Jun 16, 2024 at 2:32 PM Thomas Weißschuh <linux@xxxxxxxxxxxxxx> wrote: > > On 2024-06-16 11:12:03+0000, Thomas Weißschuh wrote: > > Instead of manually passing around 'struct edid *' and its size, > > use 'struct drm_edid', which encapsulates a validated combination of > > both. > > > > As the drm_edid_ can handle NULL gracefully, the explicit checks can be > > dropped. > > > > Also save a few characters by transforming '&array[0]' to the equivalent > > 'array' and using 'max_t(int, ...)' instead of manual casts. > > > > Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx> > > --- > > While this patch introduces a new user for drm_edid_raw(), > > if amdgpu proper gets migrated to 'struct drm_edid', that usage will go > > away. > > > > This is only compile-tested. > > > > I have some more patches for the rest of amdgpu, > > to move to 'struct drm_edid'. > > This patch is a test-balloon for the general idea. > > > > The same can also be done for drm/radeon. > > --- > > drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c | 6 +----- > > drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h | 4 ++-- > > drivers/gpu/drm/amd/amdgpu/amdgpu_vkms.c | 2 +- > > drivers/gpu/drm/amd/amdgpu/atombios_encoders.c | 21 +++++++-------------- > > drivers/gpu/drm/amd/amdgpu/dce_v10_0.c | 2 +- > > drivers/gpu/drm/amd/amdgpu/dce_v11_0.c | 2 +- > > drivers/gpu/drm/amd/amdgpu/dce_v6_0.c | 2 +- > > drivers/gpu/drm/amd/amdgpu/dce_v8_0.c | 2 +- > > 8 files changed, 15 insertions(+), 26 deletions(-) > > <snip> > > > diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c > > index 25feab188dfe..90383094ed1e 100644 > > --- a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c > > +++ b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c > > @@ -2064,20 +2064,13 @@ amdgpu_atombios_encoder_get_lcd_info(struct amdgpu_encoder *encoder) > > case LCD_FAKE_EDID_PATCH_RECORD_TYPE: > > fake_edid_record = (ATOM_FAKE_EDID_PATCH_RECORD *)record; > > if (fake_edid_record->ucFakeEDIDLength) { > > - struct edid *edid; > > - int edid_size = > > - max((int)EDID_LENGTH, (int)fake_edid_record->ucFakeEDIDLength); > > - edid = kmalloc(edid_size, GFP_KERNEL); > > - if (edid) { > > - memcpy((u8 *)edid, (u8 *)&fake_edid_record->ucFakeEDIDString[0], > > - fake_edid_record->ucFakeEDIDLength); > > - > > - if (drm_edid_is_valid(edid)) { > > - adev->mode_info.bios_hardcoded_edid = edid; > > - adev->mode_info.bios_hardcoded_edid_size = edid_size; > > - } else > > - kfree(edid); > > - } > > + const struct drm_edid *edid; > > + edid = drm_edid_alloc(fake_edid_record->ucFakeEDIDString, > > + max_t(int, EDID_LENGTH, fake_edid_record->ucFakeEDIDLength)); > > + if (drm_edid_valid(edid)) > > + adev->mode_info.bios_hardcoded_edid = edid; > > + else > > + drm_edid_free(edid); > > The old code here seems broken in general. > In drivers/gpu/drm/amd/include/atombios.h the comment for ucFakeEDIDLength says: > (I expect the same field in the same struct for amdgpu to have the same semantics) > > UCHAR ucFakeEDIDLength; // = 128 means EDID length is 128 bytes, otherwise the EDID length = ucFakeEDIDLength*128 > > So as soon as the EDID from the BIOS has extensions, only the first few > bytes will be copied into the allocated memory. drm_edid_is_valid() will > then read the uninitialized memory and if the "extensions" field ends up > non-zero it will happily "validate" past the allocated buffer. I guess the allocation should be changed to something like: if (ucFakeEDIDLength == 128) edid_size = ucFakeEDIDLength; else edid_size = ucFakeEDIDLength * 128; That said, I don't know how many systems actually used this. IIRC this was only used in GPUs from 15-20 years ago. No objections to the patch in general. Alex > > The new code won't work either but at least it won't read uninitialized > memory nor will it read past the buffer bounds. > > > } > > record += fake_edid_record->ucFakeEDIDLength ? > > struct_size(fake_edid_record, > > <snip>