Re: [PATCH] xf86drm: remove to open the DRM device unnecessarily

From: Joonyoung Shim <jy0922.shim@samsung.com>
To: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Daniel Kurtz <djkurtz@google.com>,
	cpgs@samsung.com, dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH] xf86drm: remove to open the DRM device unnecessarily
Date: Mon, 01 Jun 2015 11:53:09 +0900	[thread overview]
Message-ID: <556BC915.1080603@samsung.com> (raw)
In-Reply-To: <CACvgo50b4vKS+vQgy-nTxEv+fJibJH+Um=Pdwv9Fqx5vf+EmiQ@mail.gmail.com>

On 05/30/2015 10:20 PM, Emil Velikov wrote:
> On 29 May 2015 at 07:50, Joonyoung Shim <jy0922.shim@samsung.com> wrote:
>> On 05/29/2015 12:51 AM, Emil Velikov wrote:
>>> Seems like I'm either too subtle and/or too stingy earlier.
>>>
>>> If drmAvailable() returns false, we have two options:
>>>  - opt for the old-schoold (dri1) and ask drm_server_info to load the
>>> module for us, or
>>>  - bail out, as neither drmOpenByBusid() or drmOpenByName() will be
>>> able to open the device considering that a DRM module is not loaded.
>>>
>>> So what I was hinting earlier was to make the above more obvious,
>>> rather than reordering the arguments in the if clause. How does that
>>> sound ?
>>>
>>
>> I'm unhappy about to open DRM device always via drmAvailable(). IMHO
>> it's enough to check DRM device can be open by drmOpenByBusid() or
>> drmOpenByName() if don't load module and actually i expect DRM device
>> is open only once when call drmOpenWithType().
>>
> Seems that checking via drmAvailable() is quicker than going through
> the whole drmOpen*. On the other side the former does not cater for
> render only devices... fun.
> 

If want to check via drmAvailable(), we can call it regardless of
drmOpen*.

> Seems like this is the price to pay, considering that our current
> libdrm caters after both UMS(DRI1) and KMS(DRI2+) drivers. In the
> kernel we did have some nice cleanup (props to Daniel V and others)
> although in the userspace side things are less polished.
> 
> Perhaps we can get libdrm 3 soon or start annotating the old functions
> as depreciated ? Curious if one should add libdrm_ancient.so (or
> similar) to ensure that things don't break when building old apps
> against new libdrm ?
> 
> TLDR: No objections against the patch, but we should consider
> cleaning/splitting the ancient APIs.
> 

Agree but what i wanted to say is just to remove unnecessary to open DRM
device in drmOpen*.
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