From c18b5bdebd67112314fe73762d269d381ce3073c Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Fri, 8 May 2020 16:07:07 -0500 Subject: dmaengine: qcom: bam_dma: Replace zero-length array with flexible-array The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Reviewed-by: Jeffrey Hugo Signed-off-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20200508210707.GA24136@embeddedor Signed-off-by: Vinod Koul --- drivers/dma/qcom/bam_dma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/dma/qcom') diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c index ef73f65224b1..5a08dd0d3388 100644 --- a/drivers/dma/qcom/bam_dma.c +++ b/drivers/dma/qcom/bam_dma.c @@ -74,7 +74,7 @@ struct bam_async_desc { struct list_head desc_node; enum dma_transfer_direction dir; size_t length; - struct bam_desc_hw desc[0]; + struct bam_desc_hw desc[]; }; enum bam_reg { -- cgit v1.2.3