Hi,
On Thu, Jun 15, 2017 at 07:52:51AM +0100, Okash Khawaja wrote:
> On Wed, Jun 14, 2017 at 03:04:18PM +0200, Greg Kroah-Hartman wrote:
> > The console stuff is odd though, but that is each driver defining the
> > name for itself, major/minor does not apply. Also, a separate driver is
> > not having to figure this all out. I wonder if we could just add a tty
> > core function for this as it does know the name of everything that has
> > been registered with it, right?
>
> I can start working on a patch for this. I'm still new to the tty code
> so will follow up with any questions I might have.
I've put together this function for converting device name to number.
It traverses tty_drivers list looking for corresponding dev name and
index. Is this the right approach?
Thanks,
Okash
---
drivers/tty/tty_io.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/tty.h | 4 ++++
2 files changed, 49 insertions(+)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -325,6 +325,51 @@ static struct tty_driver *get_tty_driver
return NULL;
}
+/**
+ * tty_dev_name_to_number - return dev_t for device name
+ * @device_name: user space name of device under /dev
+ * @dev_no: pointer to dev_t that this function will populate
+ *
+ * This function converts device names like ttyS0 or ttyUSB1 into dev_t
+ * like (4, 64) or (188, 1). If no corresponding driver is registered then
+ * the function returns -ENODEV.
+ *
+ * Locking: this acquires tty_mutex
+ */
+int tty_dev_name_to_number(char *dev_name, dev_t *dev_no)
+{
+ struct tty_driver *p;
+ int rv, index, prefix_length = 0;
+
+ while (!isdigit(*(dev_name + prefix_length)) && prefix_length <
+ strlen(dev_name) )
+ prefix_length++;
+
+ if (prefix_length == strlen(dev_name))
+ return -EINVAL;
+
+ mutex_lock(&tty_mutex);
+
+ list_for_each_entry(p, &tty_drivers, tty_drivers)
+ if (prefix_length == strlen(p->name) && strncmp(dev_name,
+ p->name, prefix_length) == 0) {
+ rv = kstrtoint(dev_name + prefix_length, 10, &index);
+ if (rv) {
+ mutex_unlock(&tty_mutex);
+ return rv;
+ }
+ if (index < p->num) {
+ *dev_no = MKDEV(p->major, p->minor_start +
index);
+ mutex_unlock(&tty_mutex);
+ return 0;
+ }
+ }
+
+ mutex_unlock(&tty_mutex);
+ return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(tty_dev_name_to_number);
+
#ifdef CONFIG_CONSOLE_POLL
/**
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -402,6 +402,7 @@ extern int __init tty_init(void);
extern const char *tty_name(const struct tty_struct *tty);
extern struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode,
struct file *filp);
+extern int tty_dev_name_to_number(char *dev_name, dev_t *dev_no);
#else
static inline void tty_kref_put(struct tty_struct *tty)
{ }
@@ -422,6 +423,9 @@ static inline int __init tty_init(void)
{ return 0; }
static inline const char *tty_name(const struct tty_struct *tty)
{ return "(none)"; }
+extern int tty_dev_name_to_number(char *dev_name, dev_t *dev_no)
+{ return -ENOTSUPP; }
+
#endif
extern struct ktermios tty_std_termios;
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