Re: [PATCH v3 2/4] drm/edid: Add a function to check monitor string
From: Hsin-Yi Wang
Date: Mon Mar 04 2024 - 19:19:12 EST
On Mon, Mar 4, 2024 at 4:09 PM Jani Nikula <jani.nikula@linux.intelcom> wrote:
>
> On Mon, 04 Mar 2024, Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote:
> > On Mon, Mar 4, 2024 at 12:38 PM Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote:
> >>
> >> On Mon, 04 Mar 2024, Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> 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 <hsinyi@xxxxxxxxxxxx>
> >> > ---
> >> > 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.
> >>
> >> - 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.
> >
> > To clarify:
> > struct drm_edid currently is only internal to drm_edid.c. So with
> > change we will have to move it to the header drm_edid.h
>
> Absolutely not, struct drm_edid must remain an opaque type. The point is
> that you ask drm_edid.c if there's a match or not, and the panel code
> does not need to care what's inside struct drm_edid.
>
> >
> >>
> >> - Remove function:
> >>
> >> u32 drm_edid_get_panel_id(struct i2c_adapter *adapter);
> >>
> >
> > Probably change to u32 drm_edid_get_panel_id(const struct drm_edid
> > *);? Given that we still need to parse id from
> > drm_edid_read_base_block().
>
> No, we no longer need to parse the id outside of drm_edid.c. You'll have
> the id's in panel code in the form of struct drm_edid_ident (or
> whatever), and use the match function to see if the opaque drm_edid
> matches.
>
drm_panel prints the panel_id info on whether the panel is detected or not.
https://elixir.bootlin.com/linux/v6.8-rc7/source/drivers/gpu/drm/panel/panel-edp.c#L792
Is it okay to remove this information?
> >
> >> - Refactor edid_quirk_list to use the same id struct and match function
> >> and mechanism within drm_edid.c (can be follow-up too).
> >>
> >
> > edid_quirk currently doesn't have panel names in it, and it might be a
> > bit difficult to get all the correct names of these panels without
> > having the datasheets.
> > One way is to leave the name as null and if the name is empty and skip
> > matching the name in drm_edid_match().
>
> Exactly. NULL in drm_edid_ident would mean "don't care". I think most of
> the ones in panel code also won't use the name for matching.
>
> BR,
> Jani.
>
> >
> >> - 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
>
> --
> Jani Nikula, Intel