[PATCH v2] drm/tegra: Add tegra_gem_mmap2 to fix 64-bit offsets

[Erik Faye-Lund]

On Fri, Jan 30, 2015 at 10:49 AM, Thierry Reding
<thierry.reding at gmail.com> wrote:
> On Thu, Jan 29, 2015 at 02:18:41PM -0500, Sean Paul wrote:
>> On 64-bit targets, tegra_gem_mmap doesn't return the
>> offset to userspace. As such, subsequent calls to mmap(2)
>> fail. Add a new tegra_gem_mmap2 ioctl to fix this.
>>
>> Signed-off-by: Sean Paul <seanpaul at chromium.org>
>> ---
>>  drivers/gpu/drm/tegra/drm.c  | 21 +++++++++++++++++++++
>>  include/uapi/drm/tegra_drm.h |  9 +++++++++
>>  2 files changed, 30 insertions(+)
>
> To be honest, I'd rather just fix the existing IOCTL to do the right
> thing on 64-bit. All IOCTLs are still protected by the DRM_TEGRA_STAGING
> Kconfig symbol which depends on STAGING. We originally did that
> precisely so we'd have some leeway in fixing things up. And we've done
> precisely that in the past.
>
> The only user of this IOCTL is libdrm and I don't think that has any
> users aside from a few projects that are still under heavy development
> (like grate or the xf86-video-opentegra driver).
>
> Cc'ing Erik, who's probably the only one that's ever worked with this,
> besides me.

I also saw the patch, and had the same reaction. I'm fine with
changing the ABI, it was done already anyway
(cbfbbabb89b37f6bad05f478d906a385149f288d, "drm/tegra: Remove
gratuitous pad field"). And as you say, this is only in staging so
nobody is really relying on it, except grate and libdrm (in which this
is clearly marked as experimental). I'm fine with just changing it,
and updating grate and libdrm accordingly.