linux-kernel - Re: [PATCH] drm/komeda: Added AFBC support for komeda driver

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Date:   Fri, 24 May 2019 11:10:09 +0000
From:   Brian Starkey <Brian.Starkey@....com>
To:     "james qian wang (Arm Technology China)" <james.qian.wang@....com>
CC:     Ayan Halder <Ayan.Halder@....com>,
        Liviu Dudau <Liviu.Dudau@....com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "maarten.lankhorst@...ux.intel.com" 
        <maarten.lankhorst@...ux.intel.com>,
        "sean@...rly.run" <sean@...rly.run>,
        "Jonathan Chai (Arm Technology China)" <Jonathan.Chai@....com>,
        "Julien Yin (Arm Technology China)" <Julien.Yin@....com>,
        "thomas Sun (Arm Technology China)" <thomas.Sun@....com>,
        "Lowry Li (Arm Technology China)" <Lowry.Li@....com>,
        "Tiannan Zhu (Arm Technology China)" <Tiannan.Zhu@....com>,
        "Yiqi Kang (Arm Technology China)" <Yiqi.Kang@....com>,
        nd <nd@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/komeda: Added AFBC support for komeda driver

Hi,

On Tue, May 21, 2019 at 09:45:58AM +0100, james qian wang (Arm Technology China) wrote:
> On Thu, May 16, 2019 at 09:57:49PM +0800, Ayan Halder wrote:
> > On Thu, Apr 04, 2019 at 12:06:14PM +0100, james qian wang (Arm Technology China) wrote:
> > >  
> > > +static int
> > > +komeda_fb_afbc_size_check(struct komeda_fb *kfb, struct drm_file *file,
> > > +			  const struct drm_mode_fb_cmd2 *mode_cmd)
> > > +{
> > > +	struct drm_framebuffer *fb = &kfb->base;
> > > +	const struct drm_format_info *info = fb->format;
> > > +	struct drm_gem_object *obj;
> > > +	u32 alignment_w = 0, alignment_h = 0, alignment_header;
> > > +	u32 n_blocks = 0, min_size = 0;
> > > +
> > > +	obj = drm_gem_object_lookup(file, mode_cmd->handles[0]);
> > > +	if (!obj) {
> > > +		DRM_DEBUG_KMS("Failed to lookup GEM object\n");
> > > +		return -ENOENT;
> > > +	}
> > > +
> > > +	switch (fb->modifier & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK) {
> > > +	case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8:
> > > +		alignment_w = 32;
> > > +		alignment_h = 8;
> > > +		break;
> > > +	case AFBC_FORMAT_MOD_BLOCK_SIZE_16x16:
> > > +		alignment_w = 16;
> > > +		alignment_h = 16;
> > > +		break;
> > > +	default:
> > Can we have something like a warn here ?
> 
> will add a WARN here.
> 

I think it's better not to. fb->modifier comes from
userspace, so a malicious app could spam us with WARNs, effectively
dos-ing the system. -EINVAL should be sufficient.

Thanks,
-Brian