linux-kernel - Re: [PATCH v2] drm/edid: Implement DisplayID Type IX & X timing blocks parsing

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: <87h64xvstr.fsf@intel.com>
Date: Fri, 14 Feb 2025 10:22:40 +0200
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Egor Vorontsov <sdoregor@...re.me>, linux-kernel@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, Egor Vorontsov
 <sdoregor@...re.me>
Subject: Re: [PATCH v2] drm/edid: Implement DisplayID Type IX & X timing
 blocks parsing

On Thu, 13 Feb 2025, Egor Vorontsov <sdoregor@...re.me> wrote:
> On Wed, 2025-02-12 at 11:35 +0200, Jani Nikula wrote:
>> > +	/* TODO: support video-optimized refresh rate */
>> > +	if (timings->flags & (1 << 4))
>> > +		return NULL;
>> 
>> Mmh. I'm not sure I'd go this far. The bit indicates *two* timings, one
>> for which the below *is* correct, and another additional one with
>> vrefresh * (1000/1001).
>> 
>> We could just add a drm_dbg_kms(dev, "<message>") here about missing
>> fractional refresh rate, and proceed with the one non-fractional rate?
>> Or just have the TODO comment with no checks.
> I'll go with the former, for now.
>
>> Either way,
>> Reviewed-by: Jani Nikula <jani.nikula@...el.com>
> Thank you. ... But!
>
>> Are you up for the follow-ups too? And since you've got the hang of it,
>> maybe fix struct displayid_formula_timings_9 hactive/vactive to __be16
>> as well?
> ... at this moment I realised that both the specs and the legacy code
> actually indicate it's indeed *little*-endian shorts!
> I.e. `x[0] | x[1] << 8' -- that's LSB-first.
>
> Also, virtually no code in `drm_edid.c' uses big-endian.

Yes, I *obviously* meant __be16 and be16_to_cpu(). ;D

Good catch, and sorry about that, quite the *facepalm* for me.

> Thus, I'm fixing both my code and `displayid_detailed_timings_1' (I
> suppose you meant this struct instead) to use __le16.

Indeed.


Thanks,
Jani.


-- 
Jani Nikula, Intel