From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH libdrm] tests: fix MAKE_RGBA macro for 10bpp modes
Date: Fri, 24 Nov 2017 15:38:18 +0200 [thread overview]
Message-ID: <20171124133818.GF10981@intel.com> (raw)
In-Reply-To: <CAKb7UviveoU1AonQctaPfdY1rf+x-y_41Sh4vSF-5kO5mTEWPw@mail.gmail.com>
On Thu, Nov 23, 2017 at 03:14:46PM -0500, Ilia Mirkin wrote:
> On Thu, Nov 23, 2017 at 2:09 PM, Ville Syrjälä
> <ville.syrjala@linux.intel.com> wrote:
> > On Thu, Nov 23, 2017 at 01:59:28PM -0500, Ilia Mirkin wrote:
> >> We need to shift the values up, otherwise we'd end up with a negative
> >> shift. This works for up-to 16-bit components, which is fine for now.
> >
> > Shouldn't we actually replicate the high bits in the low bits?
>
> Not entirely sure what you're proposing...
>
> Ideally we wouldn't be lazy and pass e.g. 16-bit values to MAKE_RGBA
> which would then shift down as necessary (and even there, you could
> end up with off-by-1's maybe?). For e.g. 0xff, that should become
> 0x3ff but with my code will become 0x3fc.
Exactly the issue.
> But for other values, it's
> less clear what to do with the low bits. I figured it didn't really
> matter.
>
> Do you have a concrete proposal?
The usual thing would be just
(value) * 0x3ff / 0xff
or
((value) << 2) | ((value) >> 6)
--
Ville Syrjälä
Intel OTC
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2017-11-24 13:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-23 18:59 [PATCH libdrm] tests: fix MAKE_RGBA macro for 10bpp modes Ilia Mirkin
2017-11-23 19:09 ` Ville Syrjälä
2017-11-23 20:14 ` Ilia Mirkin
2017-11-24 13:38 ` Ville Syrjälä [this message]
2017-11-24 15:23 ` Ilia Mirkin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20171124133818.GF10981@intel.com \
--to=ville.syrjala@linux.intel.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=imirkin@alum.mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.