[RFC PATCH] pps: make number of PPS devices configurable

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

Modern systems may have more than 16 PPS sources and current hard-coded
limit breaks registration of some devices. Make the limit configurable
via Kconfig, keep default value of 16 devices. UAPI has to be changed to
support maximum possible number.

Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
---
 drivers/pps/Kconfig      | 9 +++++++++
 drivers/pps/pps.c        | 6 +++---
 include/uapi/linux/pps.h | 2 +-
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
index e1651d51cfc9..166c157505fe 100644
--- a/drivers/pps/Kconfig
+++ b/drivers/pps/Kconfig
@@ -22,6 +22,15 @@ menuconfig PPS
 
 if PPS
 
+config PPS_NR_SOURCES
+	int "Maximum number of PPS devices"
+	depends on PPS
+	range 16 256
+	default "16"
+	help
+	  Set this to the number of PPS devices you want the driver
+	  to support.
+
 config PPS_DEBUG
 	bool "PPS debugging messages"
 	help
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index de1122bb69ea..d3eac77b4cb5 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -370,7 +370,7 @@ int pps_register_cdev(struct pps_device *pps)
 	 * Get new ID for the new PPS source.  After idr_alloc() calling
 	 * the new source will be freely available into the kernel.
 	 */
-	err = idr_alloc(&pps_idr, pps, 0, PPS_MAX_SOURCES, GFP_KERNEL);
+	err = idr_alloc(&pps_idr, pps, 0, CONFIG_PPS_NR_SOURCES, GFP_KERNEL);
 	if (err < 0) {
 		if (err == -ENOSPC) {
 			pr_err("%s: too many PPS sources in the system\n",
@@ -464,7 +464,7 @@ EXPORT_SYMBOL(pps_lookup_dev);
 static void __exit pps_exit(void)
 {
 	class_unregister(&pps_class);
-	__unregister_chrdev(pps_major, 0, PPS_MAX_SOURCES, "pps");
+	__unregister_chrdev(pps_major, 0, CONFIG_PPS_NR_SOURCES, "pps");
 }
 
 static int __init pps_init(void)
@@ -477,7 +477,7 @@ static int __init pps_init(void)
 		return err;
 	}
 
-	pps_major = __register_chrdev(0, 0, PPS_MAX_SOURCES, "pps",
+	pps_major = __register_chrdev(0, 0, CONFIG_PPS_NR_SOURCES, "pps",
 				      &pps_cdev_fops);
 	if (pps_major < 0) {
 		pr_err("failed to allocate char device region\n");
diff --git a/include/uapi/linux/pps.h b/include/uapi/linux/pps.h
index 009ebcd8ced5..1088dea65e12 100644
--- a/include/uapi/linux/pps.h
+++ b/include/uapi/linux/pps.h
@@ -26,7 +26,7 @@
 #include <linux/types.h>
 
 #define PPS_VERSION		"5.3.6"
-#define PPS_MAX_SOURCES		16		/* should be enough... */
+#define PPS_MAX_SOURCES		256		/* should be enough... */
 
 /* Implementation note: the logical states ``assert'' and ``clear''
  * are implemented in terms of the chip register, i.e. ``assert''
-- 
2.47.3