Input: sysrq - DT binding for key sequence

Adding a simple device tree binding for the specification of key sequences. Definition of the keys found in the sequence are located in 'include/uapi/linux/input.h'. For the sysrq driver, holding the sequence of keys down for a specific amount of time will reset the system. Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Acked-by: Grant Likely <grant.likely@linaro.org> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: sysrq - DT binding for key sequence
Adding a simple device tree binding for the specification of key sequences. Definition of the keys found in the sequence are located in 'include/uapi/linux/input.h'. For the sysrq driver, holding the sequence of keys down for a specific amount of time will reset the system. Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Acked-by: Grant Likely <grant.likely@linaro.org> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Mathieu J. Poirier · Dmitry Torokhov
1 parent 401d7d108f
Showing 2 changed files with 75 additions and 0 deletions Side-by-side Diff
Documentation/devicetree/bindings/input/input-reset.txt
drivers/tty/sysrq.c
+Input: sysrq reset sequence
+
+A simple binding to represent a set of keys as described in
+include/uapi/linux/input.h. This is to communicate a sequence of keys to the
+sysrq driver. Upon holding the keys for a specified amount of time (if
+specified) the system is sync'ed and reset.
+
+Key sequences are global to the system but all the keys in a set must be coming
+from the same input device.
+
+The /chosen node should contain a 'linux,sysrq-reset-seq' child node to define
+a set of keys.
+
+Required property:
+sysrq-reset-seq: array of Linux keycodes, one keycode per cell.
+
+Optional property:
+timeout-ms: duration keys must be pressed together in milliseconds before
+generating a sysrq. If omitted the system is rebooted immediately when a valid
+sequence has been recognized.
+
+Example:
+
+ chosen {
+                linux,sysrq-reset-seq {
+                        keyset = <0x03
+                                  0x04
+                                  0x0a>;
+                        timeout-ms = <3000>;
+                };
+         };
+
+Would represent KEY_2, KEY_3 and KEY_9.
@@ -45,6 +45,7 @@
 #include <linux/moduleparam.h>
 #include <linux/jiffies.h>
 #include <linux/syscalls.h>
+#include <linux/of.h>
  
 #include <asm/ptrace.h>
 #include <asm/irq_regs.h>
@@ -681,6 +682,40 @@
 	}
 }
  
+#ifdef CONFIG_OF
+static void sysrq_of_get_keyreset_config(void)
+{
+	u32 key;
+	struct device_node *np;
+	struct property *prop;
+	const __be32 *p;
+
+	np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
+	if (!np) {
+		pr_debug("No sysrq node found");
+		return;
+	}
+
+	/* Reset in case a __weak definition was present */
+	sysrq_reset_seq_len = 0;
+
+	of_property_for_each_u32(np, "keyset", prop, p, key) {
+		if (key == KEY_RESERVED || key > KEY_MAX ||
+		    sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
+			break;
+
+		sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
+	}
+
+	/* Get reset timeout if any. */
+	of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
+}
+#else
+static void sysrq_of_get_keyreset_config(void)
+{
+}
+#endif
+
 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 {
 	struct sysrq_state *sysrq =
@@ -914,6 +949,7 @@
 	int error;
 	int i;
  
+	/* First check if a __weak interface was instantiated. */
 	for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
 		key = platform_sysrq_reset_seq[i];
 		if (key == KEY_RESERVED || key > KEY_MAX)
@@ -921,6 +957,12 @@
  
 		sysrq_reset_seq[sysrq_reset_seq_len++] = key;
 	}
+
+	/*
+	 * DT configuration takes precedence over anything that would
+	 * have been defined via the __weak interface.
+	 */
+	sysrq_of_get_keyreset_config();
  
 	error = input_register_handler(&sysrq_handler);
 	if (error)
	1	+Input: sysrq reset sequence
	2	+
	3	+A simple binding to represent a set of keys as described in
	4	+include/uapi/linux/input.h. This is to communicate a sequence of keys to the
	5	+sysrq driver. Upon holding the keys for a specified amount of time (if
	6	+specified) the system is sync'ed and reset.
	7	+
	8	+Key sequences are global to the system but all the keys in a set must be coming
	9	+from the same input device.
	10	+
	11	+The /chosen node should contain a 'linux,sysrq-reset-seq' child node to define
	12	+a set of keys.
	13	+
	14	+Required property:
	15	+sysrq-reset-seq: array of Linux keycodes, one keycode per cell.
	16	+
	17	+Optional property:
	18	+timeout-ms: duration keys must be pressed together in milliseconds before
	19	+generating a sysrq. If omitted the system is rebooted immediately when a valid
	20	+sequence has been recognized.
	21	+
	22	+Example:
	23	+
	24	+ chosen {
	25	+ linux,sysrq-reset-seq {
	26	+ keyset = <0x03
	27	+ 0x04
	28	+ 0x0a>;
	29	+ timeout-ms = <3000>;
	30	+ };
	31	+ };
	32	+
	33	+Would represent KEY_2, KEY_3 and KEY_9.
...	...	@@ -45,6 +45,7 @@
45	45	#include <linux/moduleparam.h>
46	46	#include <linux/jiffies.h>
47	47	#include <linux/syscalls.h>
	48	+#include <linux/of.h>
48	49
49	50	#include <asm/ptrace.h>
50	51	#include <asm/irq_regs.h>
...	...	@@ -681,6 +682,40 @@
681	682	}
682	683	}
683	684
	685	+#ifdef CONFIG_OF
	686	+static void sysrq_of_get_keyreset_config(void)
	687	+{
	688	+ u32 key;
	689	+ struct device_node *np;
	690	+ struct property *prop;
	691	+ const __be32 *p;
	692	+
	693	+ np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
	694	+ if (!np) {
	695	+ pr_debug("No sysrq node found");
	696	+ return;
	697	+ }
	698	+
	699	+ /* Reset in case a __weak definition was present */
	700	+ sysrq_reset_seq_len = 0;
	701	+
	702	+ of_property_for_each_u32(np, "keyset", prop, p, key) {
	703	+ if (key == KEY_RESERVED \|\| key > KEY_MAX \|\|
	704	+ sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
	705	+ break;
	706	+
	707	+ sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
	708	+ }
	709	+
	710	+ /* Get reset timeout if any. */
	711	+ of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
	712	+}
	713	+#else
	714	+static void sysrq_of_get_keyreset_config(void)
	715	+{
	716	+}
	717	+#endif
	718	+
684	719	static void sysrq_reinject_alt_sysrq(struct work_struct *work)
685	720	{
686	721	struct sysrq_state *sysrq =
...	...	@@ -914,6 +949,7 @@
914	949	int error;
915	950	int i;
916	951
	952	+ /* First check if a __weak interface was instantiated. */
917	953	for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
918	954	key = platform_sysrq_reset_seq[i];
919	955	if (key == KEY_RESERVED \|\| key > KEY_MAX)
...	...	@@ -921,6 +957,12 @@
921	957
922	958	sysrq_reset_seq[sysrq_reset_seq_len++] = key;
923	959	}
	960	+
	961	+ /*
	962	+ * DT configuration takes precedence over anything that would
	963	+ * have been defined via the __weak interface.
	964	+ */
	965	+ sysrq_of_get_keyreset_config();
924	966
925	967	error = input_register_handler(&sysrq_handler);
926	968	if (error)