On Mon, 4 Mar 2024 at 22:38, Jani Nikula <jani.nik...@linux.intel.com> wrote:
>
> On Mon, 04 Mar 2024, Hsin-Yi Wang <hsi...@chromium.org> wrote:
> > Add a function to check if the EDID base block contains a given string.
> >
> > One of the use cases is fetching panel from a list of panel names, since
> > some panel vendors put the monitor name after EDID_DETAIL_MONITOR_STRING
> > instead of EDID_DETAIL_MONITOR_NAME.
> >
> > Signed-off-by: Hsin-Yi Wang <hsi...@chromium.org>
> > ---
> > v2->v3: move string matching to drm_edid
> > ---
> > drivers/gpu/drm/drm_edid.c | 49 ++++++++++++++++++++++++++++++++++++++
> > include/drm/drm_edid.h | 1 +
> > 2 files changed, 50 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index 13454bc64ca2..fcdc2bd143dd 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -2789,6 +2789,55 @@ u32 drm_edid_get_panel_id(struct edid_base_block
> > *base_block)
> > }
> > EXPORT_SYMBOL(drm_edid_get_panel_id);
> >
> > +/**
> > + * drm_edid_has_monitor_string - Check if a EDID base block has certain
> > string.
> > + * @base_block: EDID base block to check.
> > + * @str: pointer to a character array to hold the string to be checked.
> > + *
> > + * Check if the detailed timings section of a EDID base block has the given
> > + * string.
> > + *
> > + * Return: True if the EDID base block contains the string, false
> > otherwise.
> > + */
> > +bool drm_edid_has_monitor_string(struct edid_base_block *base_block, const
> > char *str)
> > +{
> > + unsigned int i, j, k, buflen = strlen(str);
> > +
> > + for (i = 0; i < EDID_DETAILED_TIMINGS; i++) {
> > + struct detailed_timing *timing =
> > &base_block->edid.detailed_timings[i];
> > + unsigned int size =
> > ARRAY_SIZE(timing->data.other_data.data.str.str);
> > +
> > + if (buflen > size || timing->pixel_clock != 0 ||
> > + timing->data.other_data.pad1 != 0 ||
> > + (timing->data.other_data.type != EDID_DETAIL_MONITOR_NAME
> > &&
> > + timing->data.other_data.type !=
> > EDID_DETAIL_MONITOR_STRING))
> > + continue;
> > +
> > + for (j = 0; j < buflen; j++) {
> > + char c = timing->data.other_data.data.str.str[j];
> > +
> > + if (c != str[j] || c == '\n')
> > + break;
> > + }
> > +
> > + if (j == buflen) {
> > + /* Allow trailing white spaces. */
> > + for (k = j; k < size; k++) {
> > + char c =
> > timing->data.other_data.data.str.str[k];
> > +
> > + if (c == '\n')
> > + return true;
> > + else if (c != ' ')
> > + break;
> > + }
> > + if (k == size)
> > + return true;
> > + }
> > + }
> > +
> > + return false;
> > +}
> > +
>
> So we've put a lot of effort into converting from struct edid to struct
> drm_edid, passing that around in drm_edid.c, with the allocation size it
> provides, and generally cleaning stuff up.
>
> I'm not at all happy to see *another* struct added just for the base
> block, and detailed timing iteration as well as monitor name parsing
> duplicated.
>
> With struct drm_edid you can actually return an EDID that only has the
> base block and size 128, even if the EDID indicates more
> extensions. Because the whole thing is *designed* to handle that
> gracefully. The allocated size matters, not what the blob originating
> outside of the kernel tells you.
>
> What I'm thinking is:
>
> - Add some struct drm_edid_ident or similar. Add all the information
> that's needed to identify a panel there. I guess initially that's
> panel_id and name.
>
> struct drm_edid_ident {
> u32 panel_id;
> const char *name;
> };
>
> - Add function:
>
> bool drm_edid_match(const struct drm_edid *drm_edid, const struct
> drm_edid_ident *ident);
>
> Check if stuff in ident matches drm_edid. You can use and extend the
> existing drm_edid based iteration etc. in
> drm_edid.c. Straightforward. The fields in ident can trivially be
> extended later, and the stuff can be useful for other drivers and
> quirks etc.
That sounds perfect!
>
> - Restructure struct edp_panel_entry to contain struct
> drm_edid_ident. Change the iteration of edp_panels array to use
> drm_edid_match() on the array elements and the edid.
>
> - Add a function to read the EDID base block *but* make it return const
> struct drm_edid *. Add warnings in the comments that it's only for
> panel and for transition until it switches to reading full EDIDs.
>
> const struct drm_edid *drm_edid_read_base_block(struct i2c_adapter
> *adapter);
>
> This is the *only* hackish part of the whole thing, and it's nicely
> isolated. For the most part you can use drm_edid_get_panel_id() code
> for this, just return the blob wrapped in a struct drm_edid envelope.
>
> - Remove function:
>
> u32 drm_edid_get_panel_id(struct i2c_adapter *adapter);
>
> - Refactor edid_quirk_list to use the same id struct and match function
> and mechanism within drm_edid.c (can be follow-up too).
I wonder if we can take one step further and merge edp_panels to
edid_quirk_list (as one of the follow-ups). Maybe just some bits of
it.
> - Once you change the panel code to read the whole EDID using
> drm_edid_read family of functions in the future, you don't have to
> change *anything* about the iteration or matching or anything, because
> it's already passing struct drm_edid around.
>
>
> I hope this covers everything.
>
> BR,
> Jani.
>
>
> > /**
> > * drm_edid_get_base_block - Get a panel's EDID base block
> > * @adapter: I2C adapter to use for DDC
> > diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> > index 2455d6ab2221..248ddb0a6b5d 100644
> > --- a/include/drm/drm_edid.h
> > +++ b/include/drm/drm_edid.h
> > @@ -416,6 +416,7 @@ struct edid *drm_get_edid(struct drm_connector
> > *connector,
> > struct i2c_adapter *adapter);
> > struct edid_base_block *drm_edid_get_base_block(struct i2c_adapter
> > *adapter);
> > u32 drm_edid_get_panel_id(struct edid_base_block *base_block);
> > +bool drm_edid_has_monitor_string(struct edid_base_block *base_block, const
> > char *str);
> > struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
> > struct i2c_adapter *adapter);
> > struct edid *drm_edid_duplicate(const struct edid *edid);
>
> --
> Jani Nikula, Intel
--
With best wishes
Dmitry
