linux-kernel - Re: [PATCH v4 4/8] dmaengine: mmp_pdma: Add operations structure for controller abstraction

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Message-ID: <202508181040.az8RxLrG-lkp@intel.com>
Date: Mon, 18 Aug 2025 10:17:31 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: oe-kbuild@...ts.linux.dev, Guodong Xu <guodong@...cstar.com>,
	Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Yixun Lan <dlan@...too.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	duje@...emihanovic.xyz
Cc: lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
	Alex Elder <elder@...cstar.com>,
	Vivian Wang <wangruikang@...as.ac.cn>, dmaengine@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev,
	Guodong Xu <guodong@...cstar.com>,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: Re: [PATCH v4 4/8] dmaengine: mmp_pdma: Add operations structure for
 controller abstraction

Hi Guodong,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Guodong-Xu/dt-bindings-dma-Add-SpacemiT-K1-PDMA-controller/20250815-132049
base:   062b3e4a1f880f104a8d4b90b767788786aa7b78
patch link:    https://lore.kernel.org/r/20250815-working_dma_0701_v2-v4-4-62145ab6ea30%40riscstar.com
patch subject: [PATCH v4 4/8] dmaengine: mmp_pdma: Add operations structure for controller abstraction
config: parisc-randconfig-r072-20250818 (https://download.01.org/0day-ci/archive/20250818/202508181040.az8RxLrG-lkp@intel.com/config)
compiler: hppa-linux-gcc (GCC) 8.5.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
| Closes: https://lore.kernel.org/r/202508181040.az8RxLrG-lkp@intel.com/

smatch warnings:
drivers/dma/mmp_pdma.c:546 mmp_pdma_prep_memcpy() warn: variable dereferenced before check 'dchan' (see line 542)
drivers/dma/mmp_pdma.c:712 mmp_pdma_prep_dma_cyclic() warn: variable dereferenced before check 'dchan' (see line 708)

vim +/dchan +546 drivers/dma/mmp_pdma.c

c8acd6aa6bed3c Zhangfei Gao     2012-09-03  536  static struct dma_async_tx_descriptor *
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  537  mmp_pdma_prep_memcpy(struct dma_chan *dchan,
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  538  		     dma_addr_t dma_dst, dma_addr_t dma_src,
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  539  		     size_t len, unsigned long flags)
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  540  {
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  541  	struct mmp_pdma_chan *chan;
918da7ee50b22b Guodong Xu       2025-08-15 @542  	struct mmp_pdma_device *pdev = to_mmp_pdma_dev(dchan->device);
                                                                                                       ^^^^^^^^^^^^^
The patch adds a new dereference

c8acd6aa6bed3c Zhangfei Gao     2012-09-03  543  	struct mmp_pdma_desc_sw *first = NULL, *prev = NULL, *new;
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  544  	size_t copy = 0;
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  545  
c8acd6aa6bed3c Zhangfei Gao     2012-09-03 @546  	if (!dchan)
                                                            ^^^^^^
But the old existing code assumed dchan could be NULL

c8acd6aa6bed3c Zhangfei Gao     2012-09-03  547  		return NULL;
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  548  
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  549  	if (!len)
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  550  		return NULL;
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  551  
c8acd6aa6bed3c Zhangfei Gao     2012-09-03  552  	chan = to_mmp_pdma_chan(dchan);

[ snip ]

2b7f65b11d87f9 Joe Perches      2013-11-17  701  static struct dma_async_tx_descriptor *
2b7f65b11d87f9 Joe Perches      2013-11-17  702  mmp_pdma_prep_dma_cyclic(struct dma_chan *dchan,
2b7f65b11d87f9 Joe Perches      2013-11-17  703  			 dma_addr_t buf_addr, size_t len, size_t period_len,
2b7f65b11d87f9 Joe Perches      2013-11-17  704  			 enum dma_transfer_direction direction,
31c1e5a1350ae8 Laurent Pinchart 2014-08-01  705  			 unsigned long flags)
50440d74aae318 Daniel Mack      2013-08-21  706  {
50440d74aae318 Daniel Mack      2013-08-21  707  	struct mmp_pdma_chan *chan;
918da7ee50b22b Guodong Xu       2025-08-15 @708  	struct mmp_pdma_device *pdev = to_mmp_pdma_dev(dchan->device);
                                                                                                       ^^^^^^^^^^^^^


50440d74aae318 Daniel Mack      2013-08-21  709  	struct mmp_pdma_desc_sw *first = NULL, *prev = NULL, *new;
50440d74aae318 Daniel Mack      2013-08-21  710  	dma_addr_t dma_src, dma_dst;
50440d74aae318 Daniel Mack      2013-08-21  711  
50440d74aae318 Daniel Mack      2013-08-21 @712  	if (!dchan || !len || !period_len)
                                                            ^^^^^^
Same.


50440d74aae318 Daniel Mack      2013-08-21  713  		return NULL;
50440d74aae318 Daniel Mack      2013-08-21  714  
50440d74aae318 Daniel Mack      2013-08-21  715  	/* the buffer length must be a multiple of period_len */

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki