linux-kernel - Re: [PATCH 4/5] drm/mediatek: Add casting before assign

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Date:   Tue, 13 Jun 2023 08:26:21 +0000
From:   Jason-JH Lin (林睿祥) 
        <Jason-JH.Lin@...iatek.com>
To:     CK Hu (胡俊光) <ck.hu@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        Jason-ch Chen (陳建豪) 
        <Jason-ch.Chen@...iatek.com>,
        Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        Rex-BC Chen (陳柏辰) 
        <Rex-BC.Chen@...iatek.com>
Subject: Re: [PATCH 4/5] drm/mediatek: Add casting before assign

Hi CK,

Thanks for the reviews.

On Mon, 2023-06-12 at 09:05 +0000, CK Hu (胡俊光) wrote:
> Hi, Jason:
> 
> On Fri, 2023-04-07 at 14:46 +0800, Jason-JH.Lin wrote:
> > Add casting before assign to avoid the unintentional integer
> > overflow
> > or unintended sign extension.
> > 
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> > Fixes: 1a64a7aff8da ("drm/mediatek: Fix cursor plane no update")
> > ---
> >  drivers/gpu/drm/mediatek/mtk_drm_gem.c   |  2 +-
> >  drivers/gpu/drm/mediatek/mtk_drm_plane.c | 20 +++++++++++---------
> >  2 files changed, 12 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> > b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> > index 9b8f72ed12e4..537e83b95001 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> > @@ -121,7 +121,7 @@ int mtk_drm_gem_dumb_create(struct drm_file
> > *file_priv, struct drm_device *dev,
> >  	int ret;
> >  
> >  	args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
> > -	args->size = args->pitch * args->height;
> > +	args->size = (unsigned long)args->pitch * args->height;
> 
> The prototype is
> 
> struct drm_mode_create_dump {
> 	__u32 height;
> 	__u32 pitch;
> 	__u64 size;
> };
> 
> Do you want to case to "__u64"?
> 
Yes, it should be (unsigned long long), but I'll change it to:
args->size = (__u64)args->pitch * args->height;

> >  
> >  	mtk_gem = mtk_drm_gem_create(dev, args->size, false);
> >  	if (IS_ERR(mtk_gem))
> > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> > b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> > index 31f9420aff6f..a1337f386bbf 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> > @@ -140,7 +140,7 @@ static void mtk_plane_update_new_state(struct
> > drm_plane_state *new_state,
> >  	struct drm_framebuffer *fb = new_state->fb;
> >  	struct drm_gem_object *gem;
> >  	struct mtk_drm_gem_obj *mtk_gem;
> > -	unsigned int pitch, format;
> > +	unsigned int pitch, format, cpp;
> >  	u64 modifier;
> >  	dma_addr_t addr;
> >  	dma_addr_t hdr_addr = 0;
> > @@ -151,11 +151,12 @@ static void mtk_plane_update_new_state(struct
> > drm_plane_state *new_state,
> >  	addr = mtk_gem->dma_addr;
> >  	pitch = fb->pitches[0];
> >  	format = fb->format->format;
> > +	cpp = (unsigned int)fb->format->cpp[0];
> >  	modifier = fb->modifier;
> >  
> >  	if (modifier == DRM_FORMAT_MOD_LINEAR) {
> > -		addr += (new_state->src.x1 >> 16) * fb->format->cpp[0];
> > -		addr += (new_state->src.y1 >> 16) * pitch;
> > +		addr += (dma_addr_t)(new_state->src.x1 >> 16) * cpp;
> > +		addr += (dma_addr_t)(new_state->src.y1 >> 16) * pitch;
> >  	} else {
> >  		int width_in_blocks = ALIGN(fb->width,
> > AFBC_DATA_BLOCK_WIDTH)
> >  				      / AFBC_DATA_BLOCK_WIDTH;
> > @@ -167,17 +168,18 @@ static void mtk_plane_update_new_state(struct
> > drm_plane_state *new_state,
> >  
> >  		hdr_pitch = width_in_blocks * AFBC_HEADER_BLOCK_SIZE;
> >  		pitch = width_in_blocks * AFBC_DATA_BLOCK_WIDTH *
> > -			AFBC_DATA_BLOCK_HEIGHT * fb->format->cpp[0];
> > +			AFBC_DATA_BLOCK_HEIGHT * cpp;
> >  
> >  		hdr_size = ALIGN(hdr_pitch * height_in_blocks,
> > AFBC_HEADER_ALIGNMENT);
> >  
> > -		hdr_addr = addr + hdr_pitch * y_offset_in_blocks +
> > -			   AFBC_HEADER_BLOCK_SIZE * x_offset_in_blocks;
> > +		hdr_addr = addr +
> > +			   (dma_addr_t)hdr_pitch * y_offset_in_blocks +
> > +			   (dma_addr_t)AFBC_HEADER_BLOCK_SIZE *
> > x_offset_in_blocks;
> >  		/* The data plane is offset by 1 additional block. */
> >  		addr = addr + hdr_size +
> > -		       pitch * y_offset_in_blocks +
> > -		       AFBC_DATA_BLOCK_WIDTH * AFBC_DATA_BLOCK_HEIGHT *
> > -		       fb->format->cpp[0] * (x_offset_in_blocks + 1);
> > +		       (dma_addr_t)pitch * y_offset_in_blocks +
> > +		       (dma_addr_t)AFBC_DATA_BLOCK_WIDTH *
> > AFBC_DATA_BLOCK_HEIGHT *
> > +		       (dma_addr_t)cpp * (x_offset_in_blocks + 1);
> >  	}
> 
> I would like you to add a variable 'u32 offset' for this calculating,
> and I think u32 is enough for this calculating and it's not necessary
> to do any casting.
> 
> Regards,
> CK

I think x_offset_in_blocks and y_offset_in_blocks may be negative,
so I'll use 'int offset' for this calculating.

Regards,
Jason-JH.Lin

> 
> >  
> >  	mtk_plane_state->pending.enable = true;