[PATCH 06/18] ledtrig-blkdev: Add function to get gendisk by name

Ian Pilcher
2021-09-03T20:46:05Z

Add ledtrig_blkdev_get_disk() to find block device by name and increment
its reference count. (Caller must call put_disk().) Must be built in to
access block_class and disk_type symbols.

Add (inline) helper function to compare C string with non-terminated
character sequence (within the buffer passed to a sysfs attribute store
function).

Signed-off-by: Ian Pilcher <arequipeno@gmail.com>
---
drivers/leds/trigger/ledtrig-blkdev-core.c | 43 ++++++++++++++++++++++
drivers/leds/trigger/ledtrig-blkdev.h | 12 ++++++
2 files changed, 55 insertions(+)

diff --git a/drivers/leds/trigger/ledtrig-blkdev-core.c b/drivers/leds/trigger/ledtrig-blkdev-core.c
index 102cdbe26d66..87d439f425ad 100644
--- a/drivers/leds/trigger/ledtrig-blkdev-core.c
+++ b/drivers/leds/trigger/ledtrig-blkdev-core.c
@@ -33,3 +33,46 @@ void ledtrig_blkdev_disk_cleanup(struct gendisk *const gd)

mutex_unlock(&ledtrig_blkdev_mutex);
}
+
+
+/*
+ *
+ * ledtrig_blkdev_get_disk() - get a gendisk by name
+ *
+ * Must be built in for access to block_class and disk_type
+ * Caller must call put_disk()
+ *
+ */
+
+/* Non-null-terminated character sequence of known length */
+struct ledtrig_blkdev_gdname {
+ const char *buf;
+ size_t len;
+};
+
+/* Match function for ledtrig_blkdev_get_disk() */
+static int blkdev_match_gdname(struct device *const dev, const void *const data)
+{
+ const struct ledtrig_blkdev_gdname *const gdname = data;
+
+ if (dev->type != &disk_type)
+ return 0;
+
+ return ledtrig_blkdev_streq(dev_to_disk(dev)->disk_name,
+ gdname->buf, gdname->len);
+}
+
+struct gendisk *ledtrig_blkdev_get_disk(const char *const name,
+ const size_t len)
+{
+ const struct ledtrig_blkdev_gdname gdname = { .buf = name, .len = len };
+ struct device *dev;
+
+ dev = class_find_device(&block_class, NULL,
+ &gdname, blkdev_match_gdname);
+ if (dev == NULL)
+ return NULL;
+
+ return dev_to_disk(dev);
+}
+EXPORT_SYMBOL_NS_GPL(ledtrig_blkdev_get_disk, LEDTRIG_BLKDEV);
diff --git a/drivers/leds/trigger/ledtrig-blkdev.h b/drivers/leds/trigger/ledtrig-blkdev.h
index 914fb1523a2f..9a3528fd183a 100644
--- a/drivers/leds/trigger/ledtrig-blkdev.h
+++ b/drivers/leds/trigger/ledtrig-blkdev.h
@@ -11,5 +11,17 @@

extern struct mutex ledtrig_blkdev_mutex;
extern void (*__ledtrig_blkdev_disk_cleanup)(struct gendisk *gd);
+extern struct gendisk *ledtrig_blkdev_get_disk(const char *name, size_t len);
+
+/*
+ * Compare a null-terminated C string with a non-null-terminated character
+ * sequence of a known length. Returns true (1) if equal, false (0) if not.
+ */
+static inline bool ledtrig_blkdev_streq(const char *const cstr,
+ const char *const cbuf,
+ const size_t buf_len)
+{
+ return strlen(cstr) == buf_len && memcmp(cstr, cbuf, buf_len) == 0;
+}

#endif /* __LEDTRIG_BLKDEV_H */
--
2.31.1