linux-kernel - Re: [PATCH] drm/panel: leadtek-ltk050h3146w: transition to mipi

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAD=FV=WmPmroitmYL3a4pdw8ai2LiQpJ6=zYh0kUdqcp6463Rw@mail.gmail.com>
Date: Wed, 30 Oct 2024 10:50:14 -0700
From: Doug Anderson <dianders@...omium.org>
To: Tejas Vipin <tejasvipin76@...il.com>
Cc: neil.armstrong@...aro.org, maarten.lankhorst@...ux.intel.com, 
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch, 
	quic_jesszhan@...cinc.com, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panel: leadtek-ltk050h3146w: transition to mipi_dsi
 wrapped functions

Hi,

On Wed, Oct 30, 2024 at 12:24 AM Tejas Vipin <tejasvipin76@...il.com> wrote:
>
> On 10/29/24 12:24 AM, Doug Anderson wrote:
> > Hi,
> >
> > On Fri, Oct 25, 2024 at 9:00 PM Tejas Vipin <tejasvipin76@...il.com> wrote:
> >>
> >> @@ -418,79 +398,42 @@ static const struct ltk050h3146w_desc ltk050h3146w_data = {
> >>                 MIPI_DSI_MODE_LPM | MIPI_DSI_MODE_NO_EOT_PACKET,
> >>  };
> >>
> >> -static int ltk050h3146w_a2_select_page(struct ltk050h3146w *ctx, int page)
> >> +static void ltk050h3146w_a2_select_page(struct mipi_dsi_multi_context *dsi_ctx, int page)
> >>  {
> >> -       struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> >> -       u8 d[3] = { 0x98, 0x81, page };
> >> +       u8 d[4] = { 0xff, 0x98, 0x81, page };
> >>
> >> -       return mipi_dsi_dcs_write(dsi, 0xff, d, ARRAY_SIZE(d));
> >> +       mipi_dsi_dcs_write_buffer_multi(dsi_ctx, d, ARRAY_SIZE(d));
> >
> > FWIW: the above might be slightly better as:
> >
> > mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xff, 0x98, 0x81, page);
> >
> > That would make it more documenting that the 0xff is the "cmd", has
> > fewer lines of code, and also gets the array marked as "static const"
> > which might make the compiler slightly more efficient. ;-)
> >
> > Not really a huge deal, though.
> >
>
> I did try this initially, but got an error because of page not being a
> compile time constant. Not sure how I should handle this.

Ha, that makes sense! It can't be "static const" because that means
that there's one storage location that's never changing and that's
just not true. I tried to see if there was some way to make the
mipi_dsi_dcs_write_seq_multi() smarter and have it detect if
everything is constant but I couldn't find any way to do that. The
__builtin_constant_p() trick doesn't seem to work with more than one
number.

So I think what you have is fine then. If this becomes common I guess
we can make an alternative version of mipi_dsi_dcs_write_seq_multi()
that just uses "const" instead of "static const".

I'll plan to apply your patch next week unless someone beats me to it.

-Doug