summaryrefslogtreecommitdiff
path: root/target/linux/brcm2708/patches-4.4/0039-Add-dev-gpiomem-device-for-rootless-user-GPIO-access.patch
blob: f4bd017b26f7f5f8d76fd2232354049b4804d853 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
From 1ee3b49a62efe1416a6b40fb5c6032288f3d2b08 Mon Sep 17 00:00:00 2001
From: Luke Wren <luke@raspberrypi.org>
Date: Fri, 21 Aug 2015 23:14:48 +0100
Subject: [PATCH 039/232] Add /dev/gpiomem device for rootless user GPIO access

Signed-off-by: Luke Wren <luke@raspberrypi.org>

bcm2835-gpiomem: Fix for ARCH_BCM2835 builds

Build on ARCH_BCM2835, and fail to probe if no IO resource.

See: https://github.com/raspberrypi/linux/issues/1154
---
 drivers/char/broadcom/Kconfig           |   9 ++
 drivers/char/broadcom/Makefile          |   3 +
 drivers/char/broadcom/bcm2835-gpiomem.c | 260 ++++++++++++++++++++++++++++++++
 3 files changed, 272 insertions(+)
 create mode 100644 drivers/char/broadcom/bcm2835-gpiomem.c

--- a/drivers/char/broadcom/Kconfig
+++ b/drivers/char/broadcom/Kconfig
@@ -32,3 +32,12 @@ config BCM_VC_SM
 	help
 	Support for the VC shared memory on the Broadcom reference
 	design. Uses the VCHIQ stack.
+
+config BCM2835_DEVGPIOMEM
+	tristate "/dev/gpiomem rootless GPIO access via mmap() on the BCM2835"
+	default m
+	help
+		Provides users with root-free access to the GPIO registers
+		on the 2835. Calling mmap(/dev/gpiomem) will map the GPIO
+		register page to the user's pointer.
+
--- a/drivers/char/broadcom/Makefile
+++ b/drivers/char/broadcom/Makefile
@@ -1,3 +1,6 @@
 obj-$(CONFIG_BCM_VC_CMA)	+= vc_cma/
 obj-$(CONFIG_BCM2708_VCMEM)	+= vc_mem.o
 obj-$(CONFIG_BCM_VC_SM)         += vc_sm/
+
+obj-$(CONFIG_BCM2835_DEVGPIOMEM)+= bcm2835-gpiomem.o
+
--- /dev/null
+++ b/drivers/char/broadcom/bcm2835-gpiomem.c
@@ -0,0 +1,260 @@
+/**
+ * GPIO memory device driver
+ *
+ * Creates a chardev /dev/gpiomem which will provide user access to
+ * the BCM2835's GPIO registers when it is mmap()'d.
+ * No longer need root for user GPIO access, but without relaxing permissions
+ * on /dev/mem.
+ *
+ * Written by Luke Wren <luke@raspberrypi.org>
+ * Copyright (c) 2015, Raspberry Pi (Trading) Ltd.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions, and the following disclaimer,
+ *    without modification.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The names of the above-listed copyright holders may not be used
+ *    to endorse or promote products derived from this software without
+ *    specific prior written permission.
+ *
+ * ALTERNATIVELY, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2, as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/cdev.h>
+#include <linux/pagemap.h>
+#include <linux/io.h>
+
+#define DEVICE_NAME "bcm2835-gpiomem"
+#define DRIVER_NAME "gpiomem-bcm2835"
+#define DEVICE_MINOR 0
+
+struct bcm2835_gpiomem_instance {
+	unsigned long gpio_regs_phys;
+	struct device *dev;
+};
+
+static struct cdev bcm2835_gpiomem_cdev;
+static dev_t bcm2835_gpiomem_devid;
+static struct class *bcm2835_gpiomem_class;
+static struct device *bcm2835_gpiomem_dev;
+static struct bcm2835_gpiomem_instance *inst;
+
+
+/****************************************************************************
+*
+*   GPIO mem chardev file ops
+*
+***************************************************************************/
+
+static int bcm2835_gpiomem_open(struct inode *inode, struct file *file)
+{
+	int dev = iminor(inode);
+	int ret = 0;
+
+	dev_info(inst->dev, "gpiomem device opened.");
+
+	if (dev != DEVICE_MINOR) {
+		dev_err(inst->dev, "Unknown minor device: %d", dev);
+		ret = -ENXIO;
+	}
+	return ret;
+}
+
+static int bcm2835_gpiomem_release(struct inode *inode, struct file *file)
+{
+	int dev = iminor(inode);
+	int ret = 0;
+
+	if (dev != DEVICE_MINOR) {
+		dev_err(inst->dev, "Unknown minor device %d", dev);
+		ret = -ENXIO;
+	}
+	return ret;
+}
+
+static const struct vm_operations_struct bcm2835_gpiomem_vm_ops = {
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+	.access = generic_access_phys
+#endif
+};
+
+static int bcm2835_gpiomem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	/* Ignore what the user says - they're getting the GPIO regs
+	   whether they like it or not! */
+	unsigned long gpio_page = inst->gpio_regs_phys >> PAGE_SHIFT;
+
+	vma->vm_page_prot = phys_mem_access_prot(file, gpio_page,
+						 PAGE_SIZE,
+						 vma->vm_page_prot);
+	vma->vm_ops = &bcm2835_gpiomem_vm_ops;
+	if (remap_pfn_range(vma, vma->vm_start,
+			gpio_page,
+			PAGE_SIZE,
+			vma->vm_page_prot)) {
+		return -EAGAIN;
+	}
+	return 0;
+}
+
+static const struct file_operations
+bcm2835_gpiomem_fops = {
+	.owner = THIS_MODULE,
+	.open = bcm2835_gpiomem_open,
+	.release = bcm2835_gpiomem_release,
+	.mmap = bcm2835_gpiomem_mmap,
+};
+
+
+ /****************************************************************************
+*
+*   Probe and remove functions
+*
+***************************************************************************/
+
+
+static int bcm2835_gpiomem_probe(struct platform_device *pdev)
+{
+	int err;
+	void *ptr_err;
+	struct device *dev = &pdev->dev;
+	struct resource *ioresource;
+
+	/* Allocate buffers and instance data */
+
+	inst = kzalloc(sizeof(struct bcm2835_gpiomem_instance), GFP_KERNEL);
+
+	if (!inst) {
+		err = -ENOMEM;
+		goto failed_inst_alloc;
+	}
+
+	inst->dev = dev;
+
+	ioresource = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (ioresource) {
+		inst->gpio_regs_phys = ioresource->start;
+	} else {
+		dev_err(inst->dev, "failed to get IO resource");
+		err = -ENOENT;
+		goto failed_get_resource;
+	}
+
+	/* Create character device entries */
+
+	err = alloc_chrdev_region(&bcm2835_gpiomem_devid,
+				  DEVICE_MINOR, 1, DEVICE_NAME);
+	if (err != 0) {
+		dev_err(inst->dev, "unable to allocate device number");
+		goto failed_alloc_chrdev;
+	}
+	cdev_init(&bcm2835_gpiomem_cdev, &bcm2835_gpiomem_fops);
+	bcm2835_gpiomem_cdev.owner = THIS_MODULE;
+	err = cdev_add(&bcm2835_gpiomem_cdev, bcm2835_gpiomem_devid, 1);
+	if (err != 0) {
+		dev_err(inst->dev, "unable to register device");
+		goto failed_cdev_add;
+	}
+
+	/* Create sysfs entries */
+
+	bcm2835_gpiomem_class = class_create(THIS_MODULE, DEVICE_NAME);
+	ptr_err = bcm2835_gpiomem_class;
+	if (IS_ERR(ptr_err))
+		goto failed_class_create;
+
+	bcm2835_gpiomem_dev = device_create(bcm2835_gpiomem_class, NULL,
+					bcm2835_gpiomem_devid, NULL,
+					"gpiomem");
+	ptr_err = bcm2835_gpiomem_dev;
+	if (IS_ERR(ptr_err))
+		goto failed_device_create;
+
+	dev_info(inst->dev, "Initialised: Registers at 0x%08lx",
+		inst->gpio_regs_phys);
+
+	return 0;
+
+failed_device_create:
+	class_destroy(bcm2835_gpiomem_class);
+failed_class_create:
+	cdev_del(&bcm2835_gpiomem_cdev);
+	err = PTR_ERR(ptr_err);
+failed_cdev_add:
+	unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
+failed_alloc_chrdev:
+failed_get_resource:
+	kfree(inst);
+failed_inst_alloc:
+	dev_err(inst->dev, "could not load bcm2835_gpiomem");
+	return err;
+}
+
+static int bcm2835_gpiomem_remove(struct platform_device *pdev)
+{
+	struct device *dev = inst->dev;
+
+	kfree(inst);
+	device_destroy(bcm2835_gpiomem_class, bcm2835_gpiomem_devid);
+	class_destroy(bcm2835_gpiomem_class);
+	cdev_del(&bcm2835_gpiomem_cdev);
+	unregister_chrdev_region(bcm2835_gpiomem_devid, 1);
+
+	dev_info(dev, "GPIO mem driver removed - OK");
+	return 0;
+}
+
+ /****************************************************************************
+*
+*   Register the driver with device tree
+*
+***************************************************************************/
+
+static const struct of_device_id bcm2835_gpiomem_of_match[] = {
+	{.compatible = "brcm,bcm2835-gpiomem",},
+	{ /* sentinel */ },
+};
+
+MODULE_DEVICE_TABLE(of, bcm2835_gpiomem_of_match);
+
+static struct platform_driver bcm2835_gpiomem_driver = {
+	.probe = bcm2835_gpiomem_probe,
+	.remove = bcm2835_gpiomem_remove,
+	.driver = {
+		   .name = DRIVER_NAME,
+		   .owner = THIS_MODULE,
+		   .of_match_table = bcm2835_gpiomem_of_match,
+		   },
+};
+
+module_platform_driver(bcm2835_gpiomem_driver);
+
+MODULE_ALIAS("platform:gpiomem-bcm2835");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("gpiomem driver for accessing GPIO from userspace");
+MODULE_AUTHOR("Luke Wren <luke@raspberrypi.org>");