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authorLinus Torvalds <torvalds@linux-foundation.org>2026-08-19 10:09:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2026-08-19 10:09:22 -0700
commitf4cdf7ca9a1fdcca413157df19753f388a5a224e (patch)
tree60a31895b2446cd7fa27514e8c2843534a0de0da /samples/kfifo/dma-example.c
downloadlinux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.tar.gz
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Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-mediagrafted
Pull media updates from Mauro Carvalho Chehab: - v4l2-core: added ISP statistics support and per-block validation - v4l2-core: Allow unknown HDR10 white point and luminance - New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor - New codec: Milos: VPU v2.0 codec support - isp driver: gained support for Dreamchip RPPX1 ISP framework - vsp1 driver: gained support for RZ/T2H and RZ/N2H - Novalake driver: gained CVS support for new NVL hardware - dvb-core: fix feed leak on failed DMX_ADD_PID - several driver fixes, cleanups and minor improvements * tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits) media: ipu-bridge: check all DMI entries when overriding sensor rotation media: v4l2-async: avoid deleting unlinked ASC entry on link error media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement media: intel/ipu6: fix async notifier cleanup leak on parse error media: staging/ipu7: fix async notifier UAF on probe error path media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem() media: rcar-isp: Fix VSPX reference leaks media: rcar-isp: Release ISPCORE resources media: i2c: imx415: Release runtime PM reference on VBLANK error media: i2c: imx415: Return test pattern write errors media: renesas: vsp1: Declare index variables in for loop statement media: renesas: vsp1: Make reset control optional to support platforms without a reset line media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs media: nxp: imx8-isi: Add additional 32-bit RGB format support media: nxp: imx8-isi: Add 16-bit raw Bayer format support media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks media: nxp: imx8-isi: Correct color map between V4L2 and ISI ...
Diffstat (limited to 'samples/kfifo/dma-example.c')
-rw-r--r--samples/kfifo/dma-example.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/samples/kfifo/dma-example.c b/samples/kfifo/dma-example.c
new file mode 100644
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+++ b/samples/kfifo/dma-example.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Sample fifo dma implementation
+ *
+ * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
+ */
+
+#include <linux/init.h>
+#include <linux/kfifo.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/dma-mapping.h>
+
+/*
+ * This module shows how to handle fifo dma operations.
+ */
+
+/* fifo size in elements (bytes) */
+#define FIFO_SIZE 32
+
+static struct kfifo fifo;
+
+static int __init example_init(void)
+{
+ int i;
+ unsigned int ret;
+ unsigned int nents;
+ struct scatterlist sg[10];
+
+ printk(KERN_INFO "DMA fifo test start\n");
+
+ if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) {
+ printk(KERN_WARNING "error kfifo_alloc\n");
+ return -ENOMEM;
+ }
+
+ printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo));
+
+ kfifo_in(&fifo, "test", 4);
+
+ for (i = 0; i != 9; i++)
+ kfifo_put(&fifo, i);
+
+ /* kick away first byte */
+ kfifo_skip(&fifo);
+
+ printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
+
+ /*
+ * Configure the kfifo buffer to receive data from DMA input.
+ *
+ * .--------------------------------------.
+ * | 0 | 1 | 2 | ... | 12 | 13 | ... | 31 |
+ * |---|------------------|---------------|
+ * \_/ \________________/ \_____________/
+ * \ \ \
+ * \ \_allocated data \
+ * \_*free space* \_*free space*
+ *
+ * We need two different SG entries: one for the free space area at the
+ * end of the kfifo buffer (19 bytes) and another for the first free
+ * byte at the beginning, after the kfifo_skip().
+ */
+ sg_init_table(sg, ARRAY_SIZE(sg));
+ nents = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
+ printk(KERN_INFO "DMA sgl entries: %d\n", nents);
+ if (!nents) {
+ /* fifo is full and no sgl was created */
+ printk(KERN_WARNING "error kfifo_dma_in_prepare\n");
+ return -EIO;
+ }
+
+ /* receive data */
+ printk(KERN_INFO "scatterlist for receive:\n");
+ for (i = 0; i < nents; i++) {
+ printk(KERN_INFO
+ "sg[%d] -> "
+ "page %p offset 0x%.8x length 0x%.8x\n",
+ i, sg_page(&sg[i]), sg[i].offset, sg[i].length);
+
+ if (sg_is_last(&sg[i]))
+ break;
+ }
+
+ /* put here your code to setup and exectute the dma operation */
+ /* ... */
+
+ /* example: zero bytes received */
+ ret = 0;
+
+ /* finish the dma operation and update the received data */
+ kfifo_dma_in_finish(&fifo, ret);
+
+ /* Prepare to transmit data, example: 8 bytes */
+ nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);
+ printk(KERN_INFO "DMA sgl entries: %d\n", nents);
+ if (!nents) {
+ /* no data was available and no sgl was created */
+ printk(KERN_WARNING "error kfifo_dma_out_prepare\n");
+ return -EIO;
+ }
+
+ printk(KERN_INFO "scatterlist for transmit:\n");
+ for (i = 0; i < nents; i++) {
+ printk(KERN_INFO
+ "sg[%d] -> "
+ "page %p offset 0x%.8x length 0x%.8x\n",
+ i, sg_page(&sg[i]), sg[i].offset, sg[i].length);
+
+ if (sg_is_last(&sg[i]))
+ break;
+ }
+
+ /* put here your code to setup and exectute the dma operation */
+ /* ... */
+
+ /* example: 5 bytes transmitted */
+ ret = 5;
+
+ /* finish the dma operation and update the transmitted data */
+ kfifo_dma_out_finish(&fifo, ret);
+
+ ret = kfifo_len(&fifo);
+ printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
+
+ if (ret != 7) {
+ printk(KERN_WARNING "size mismatch: test failed");
+ return -EIO;
+ }
+ printk(KERN_INFO "test passed\n");
+
+ return 0;
+}
+
+static void __exit example_exit(void)
+{
+ kfifo_free(&fifo);
+}
+
+module_init(example_init);
+module_exit(example_exit);
+MODULE_DESCRIPTION("Sample fifo dma implementation");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");