From: Rosen Penev Date: Sun, 31 May 2026 02:08:43 +0000 (-0700) Subject: dmaengine: ste_dma40: turn d40_base phy_chans into a flexible array X-Git-Tag: v7.2-rc1~55^2~24 X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=cc4fea19daeb0460fe3569e0a2d523f427b2bac1;p=thirdparty%2Fkernel%2Flinux.git dmaengine: ste_dma40: turn d40_base phy_chans into a flexible array Convert the separately-offset phy_chans pointer to a C99 flexible array member at the end of struct d40_base, and switch the allocation to struct_size(). The log_chans and memcpy_chans slots continue to live in the same allocation immediately after phy_chans, indexed via base->log_chans. This removes the hand-rolled pointer fixup that recomputed phy_chans from base + ALIGN(sizeof(struct d40_base), 4). The ALIGN(sizeof(struct d40_base), 4) requirement is met implicitly by the C compiler when using a flexible array member. With struct d40_chan phy_chans[] as the last member, the C standard guarantees sizeof(struct d40_base) includes trailing padding to satisfy the alignment of the flexible array element type (struct d40_chan). Since struct d40_chan contains members like spinlock_t, pointers, and struct dma_chan — all with alignment ≥ 4 — the compiler ensures sizeof(struct d40_base) is already a multiple of _Alignof(struct d40_chan) >= 4. The struct_size() macro then computes sizeof(struct d40_base) + sizeof(struct d40_chan) * num_phy_chans, so phy_chans[0] lands at a properly aligned offset without needing the manual ALIGN. Assisted-by: Claude:Opus-4.7 Signed-off-by: Rosen Penev Reviewed-by: Linus Walleij Link: https://patch.msgid.link/20260531020843.594892-1-rosenp@gmail.com Signed-off-by: Vinod Koul --- diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c index 9b803c0aec254..0d9ffa3e26639 100644 --- a/drivers/dma/ste_dma40.c +++ b/drivers/dma/ste_dma40.c @@ -602,7 +602,6 @@ struct d40_base { struct dma_device dma_both; struct dma_device dma_slave; struct dma_device dma_memcpy; - struct d40_chan *phy_chans; struct d40_chan *log_chans; struct d40_chan **lookup_log_chans; struct d40_chan **lookup_phy_chans; @@ -621,6 +620,7 @@ struct d40_base { u32 *regs_interrupt; u16 gcc_pwr_off_mask; struct d40_gen_dmac gen_dmac; + struct d40_chan phy_chans[]; }; static struct device *chan2dev(struct d40_chan *d40c) @@ -3128,6 +3128,7 @@ static int __init d40_hw_detect_init(struct platform_device *pdev, struct clk *clk; void __iomem *virtbase; struct d40_base *base; + size_t alloc_size; int num_log_chans; int num_phy_chans; int num_memcpy_chans; @@ -3185,22 +3186,24 @@ static int __init d40_hw_detect_init(struct platform_device *pdev, else num_phy_chans = 4 * (readl(virtbase + D40_DREG_ICFG) & 0x7) + 4; + num_phy_chans = min(num_phy_chans, STEDMA40_MAX_PHYS); + /* The number of channels used for memcpy */ if (plat_data->num_of_memcpy_chans) num_memcpy_chans = plat_data->num_of_memcpy_chans; else num_memcpy_chans = ARRAY_SIZE(dma40_memcpy_channels); + num_memcpy_chans = min(num_memcpy_chans, D40_MEMCPY_MAX_CHANS); num_log_chans = num_phy_chans * D40_MAX_LOG_CHAN_PER_PHY; dev_info(dev, "hardware rev: %d with %d physical and %d logical channels\n", rev, num_phy_chans, num_log_chans); - base = devm_kzalloc(dev, - ALIGN(sizeof(struct d40_base), 4) + - (num_phy_chans + num_log_chans + num_memcpy_chans) * - sizeof(struct d40_chan), GFP_KERNEL); + alloc_size = struct_size(base, phy_chans, num_phy_chans); + alloc_size += sizeof(*base->log_chans) * (num_log_chans + num_memcpy_chans); + base = devm_kzalloc(dev, alloc_size, GFP_KERNEL); if (!base) return -ENOMEM; @@ -3213,7 +3216,6 @@ static int __init d40_hw_detect_init(struct platform_device *pdev, base->virtbase = virtbase; base->plat_data = plat_data; base->dev = dev; - base->phy_chans = ((void *)base) + ALIGN(sizeof(struct d40_base), 4); base->log_chans = &base->phy_chans[num_phy_chans]; if (base->plat_data->num_of_phy_chans == 14) {