linux-kernel - Re: [PATCH] dma: xilinx-vdma: add some sanity checks

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Date:	Mon, 13 Jun 2016 22:32:29 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Dan Williams <dan.j.williams@...el.com>,
	Michal Simek <michal.simek@...inx.com>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	Kedareswara rao Appana <appana.durga.rao@...inx.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma: xilinx-vdma: add some sanity checks

On Mon, Jun 13, 2016 at 05:07:33PM +0200, Arnd Bergmann wrote:
> The newly added xilinx_dma_prep_dma_cyclic function sometimes causes
> a gcc warning about the use of the segment function in case
> we never run into the inner loop of the function:
> 
> dma/xilinx/xilinx_vdma.c: In function 'xilinx_dma_prep_dma_cyclic':
> dma/xilinx/xilinx_vdma.c:1808:23: error: 'segment' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>    segment->hw.control |= XILINX_DMA_BD_SOP;
> 
> This can only happen if the period len is zero (which would cause other
> problems earlier), or if the buffer is shorter than a period. Neither
> of them should ever happen, but by adding an explicit check for these two
> cases, we can abort in a more controlled way, and the compiler is
> able to see that we never use uninitialized data.

Applied after fixing subsystem name

Thanks
-- 
~Vinod