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authorLinus Torvalds <torvalds@linux-foundation.org>2026-08-24 08:46:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2026-08-24 08:46:03 -0700
commitcf9610f9116d55c5a66ef9f1faecacabd93a9322 (patch)
tree757a3d280760c654767631cab5ad8af2d86d1848 /samples/kfifo/dma-example.c
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Merge tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrlgrafted
Pull pin control updates from Linus Walleij: "Core changes: - Use the non-blocking mux_state_try_select() in the generic MUX pin control back-end - Free pin maps on pinctrl_generic_to_map() failure in the core helpers New hardware pin control: - Qualcomm Maili TLMM SoC, PMG1110 PMIC, and Eliza LPASS LPI TLMM SoC (this is for the low power audio, LPASS = Low Power Audio SubSystem portions) - Upboard support on top of the Intel pin controller - Apple T6030 and T6031 support (just compatible strings) - Samsung Exynos 8855 SoC - Mediatek MT6858 SoC - Rockchip RK3308B and RV1106 SoCs - Airoha EN7523 and AN7563 SoCs Improvements: - Qualcomm TLMM GPIOs are unconditionally marked as wakeup capable - Qualcomm improvements on top of the Qualcomm PDC (power domain controller) irqchip improvements from tglx:s tree - Qualcomm IPQ806x and IPQ9650 non-urgent pin grop fixups - The NPCM8xx driver has been put into shape fixing many pin and group definitions - Some non-urgent Tegra 264 pin assignments are fixed up - Some non-urgent fixups to Airoha AN7581 and AN7583 registers and pin assignments, missing features etc" * tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl: (130 commits) dt-bindings: pinctrl: Convert TI DA850 pupd to DT schema pinctrl: meson: sync some modify from A4 pinctrl: meson: a4: Add input enable pin configuration pinctrl: realtek: rtd1625: remove unused group name spdif_sel pinctrl: realtek: rtd1625: fix base_bit for VE4 GPIO 13 dt-bindings: pinctrl: microchip,pic32mzda-pinctrl: Convert to DT schema Revert "Merge branch 'ib-rsk7204' into devel" pinctrl: rockchip: Add RV1106 pinctrl support dt-bindings: pinctrl: rockchip: Add RV1106 compatible pinctrl: rockchip: Decode drive strength in the get function pinctrl: fix PINCTRL_GENERIC_MUX not always being selectable pinctrl: airoha: add support of an7563 SoC dt-bindings: pinctrl: airoha: add support of an7563 pin controller pinctrl: airoha: try to find chip scu node by phandle first pinctrl: airoha: add support of en7523 SoC dt-bindings: pinctrl: airoha: add support of en7523 pin controller pinctrl: airoha: an7583: add support for olt pinmux pinctrl: airoha: an7583: add support for pon_alt pinmux pinctrl: airoha: an7583: add support for npu_uart pinmux dt-bindings: pinctrl: airoha: an7583: add missed features ...
Diffstat (limited to 'samples/kfifo/dma-example.c')
-rw-r--r--samples/kfifo/dma-example.c144
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diff --git a/samples/kfifo/dma-example.c b/samples/kfifo/dma-example.c
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+// 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>");