[PATCH v1 03/15] auxdisplay: linedisp: Use unique number for id

Andy Shevchenko
2024-02-08T18:49:27Z

The absence of decrementation of linedisp_id is incorrect in two ways,
i.e. it may cause:
- an ID exhaustion
- (and if the above is addressed) a duplicate id number may be allocated
next time a device is added

Replace above mentioned approach by using IDA framework.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
drivers/auxdisplay/line-display.c | 13 ++++++++++---
drivers/auxdisplay/line-display.h | 2 ++
2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/auxdisplay/line-display.c b/drivers/auxdisplay/line-display.c
index 310e9bfb41ae..c4dbb13293d1 100644
--- a/drivers/auxdisplay/line-display.c
+++ b/drivers/auxdisplay/line-display.c
@@ -11,6 +11,7 @@
#include <generated/utsrelease.h>

#include <linux/device.h>
+#include <linux/idr.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
@@ -188,11 +189,14 @@ static struct attribute *linedisp_attrs[] = {
};
ATTRIBUTE_GROUPS(linedisp);

+static DEFINE_IDA(linedisp_id);
+
static void linedisp_release(struct device *dev)
{
struct linedisp *linedisp = container_of(dev, struct linedisp, dev);

kfree(linedisp->message);
+ ida_free(&linedisp_id, linedisp->id);
}

static const struct device_type linedisp_type = {
@@ -214,7 +218,6 @@ int linedisp_register(struct linedisp *linedisp, struct device *parent,
unsigned int num_chars, char *buf,
void (*update)(struct linedisp *linedisp))
{
- static atomic_t linedisp_id = ATOMIC_INIT(-1);
int err;

memset(linedisp, 0, sizeof(*linedisp));
@@ -225,9 +228,13 @@ int linedisp_register(struct linedisp *linedisp, struct device *parent,
linedisp->num_chars = num_chars;
linedisp->scroll_rate = DEFAULT_SCROLL_RATE;

+ err = ida_alloc(&linedisp_id, GFP_KERNEL);
+ if (err < 0)
+ return err;
+ linedisp->id = err;
+
device_initialize(&linedisp->dev);
- dev_set_name(&linedisp->dev, "linedisp.%lu",
- (unsigned long)atomic_inc_return(&linedisp_id));
+ dev_set_name(&linedisp->dev, "linedisp.%u", linedisp->id);

/* initialise a timer for scrolling the message */
timer_setup(&linedisp->timer, linedisp_scroll, 0);
diff --git a/drivers/auxdisplay/line-display.h b/drivers/auxdisplay/line-display.h
index 0f5891d34c48..1fbe57fdc4cb 100644
--- a/drivers/auxdisplay/line-display.h
+++ b/drivers/auxdisplay/line-display.h
@@ -14,6 +14,7 @@
/**
* struct linedisp - character line display private data structure
* @dev: the line display device
+ * @id: instance id of this display
* @timer: timer used to implement scrolling
* @update: function called to update the display
* @buf: pointer to the buffer for the string currently displayed
@@ -25,6 +26,7 @@
*/
struct linedisp {
struct device dev;
+ unsigned int id;
struct timer_list timer;
void (*update)(struct linedisp *linedisp);
char *buf;
--
2.43.0.rc1.1.gbec44491f096