Subject: Re: [PATCH] staging/android: refactor SYNC_IOC_FILE_INFO
To: Gustavo Padovan <gustavo@padovan.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
References: <1456948331-7300-5-git-send-email-gustavo@padovan.org>
 <1457015665-7534-1-git-send-email-gustavo@padovan.org>
Cc: linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org,
        dri-devel@lists.freedesktop.org, Daniel Stone <daniels@collabora.com>,
        =?UTF-8?Q?Arve_Hj=c3=b8nnev=c3=a5g?= <arve@android.com>,
        Riley Andrews <riandrews@android.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Rob Clark <robdclark@gmail.com>, Greg Hackmann <ghackmann@google.com>,
        John Harrison <John.C.Harrison@Intel.com>,
        Gustavo Padovan <gustavo.padovan@collabora.co.uk>
From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Message-ID: <56D85161.6070503@linux.intel.com>
Date: Thu, 3 Mar 2016 15:59:45 +0100
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Op 03-03-16 om 15:34 schreef Gustavo Padovan:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>
> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> optimize buffer
>
> Now num_fences can be filled by the caller to inform how many fences it
> wants to retrieve from the kernel. If the num_fences passed is greater
> than zero info->sync_fence_info should point to a buffer with enough space
> to fit all fences.
>
> However if num_fences passed to the kernel is 0, the kernel will reply
> with number of fences of the sync_file.
>
> Sending first an ioctl with num_fences = 0 can optimize buffer allocation,
> in a first call with num_fences = 0 userspace will receive the actual
> number of fences in the num_fences filed.
>
> Then it can allocate a buffer with the correct size on sync_fence_info and
> call SYNC_IOC_FILE_INFO again, but now with the actual value of num_fences
> in the sync_file.
>
> Also, info->sync_fence_info was converted to __u64 pointer to prevent
> 32bit compatibility issues.
For this patch and 6/6:

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>