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Subject[PATCH v2 1/2] serial: pl010: Move uart_register_driver call to device probe
Date
uart_register_driver call binds the driver to a specific device
node through tty_register_driver call. This should typically
happen during device probe call.

In a multiplatform scenario, it is possible that multiple serial
drivers are part of the kernel. Currently the driver registration fails
if multiple serial drivers with overlapping major/minor numbers are
included.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>

---

Changes in v2:
- Add locking to prevent issues when two probes run in parallel

drivers/tty/serial/amba-pl010.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/amba-pl010.c b/drivers/tty/serial/amba-pl010.c
index f2f251075109..24180adb1cbb 100644
--- a/drivers/tty/serial/amba-pl010.c
+++ b/drivers/tty/serial/amba-pl010.c
@@ -697,6 +697,7 @@ static struct console amba_console = {
#define AMBA_CONSOLE NULL
#endif

+static DEFINE_MUTEX(amba_reg_lock);
static struct uart_driver amba_reg = {
.owner = THIS_MODULE,
.driver_name = "ttyAM",
@@ -749,6 +750,19 @@ static int pl010_probe(struct amba_device *dev, const struct amba_id *id)
amba_ports[i] = uap;

amba_set_drvdata(dev, uap);
+
+ mutex_lock(&amba_reg_lock);
+ if (!amba_reg.state) {
+ ret = uart_register_driver(&amba_reg);
+ if (ret < 0) {
+ mutex_unlock(&amba_reg_lock);
+ dev_err(uap->port.dev,
+ "Failed to register AMBA-PL010 driver\n");
+ return ret;
+ }
+ }
+ mutex_unlock(&amba_reg_lock);
+
ret = uart_add_one_port(&amba_reg, &uap->port);
if (ret)
amba_ports[i] = NULL;
@@ -760,12 +774,18 @@ static int pl010_remove(struct amba_device *dev)
{
struct uart_amba_port *uap = amba_get_drvdata(dev);
int i;
+ bool busy = false;

uart_remove_one_port(&amba_reg, &uap->port);

for (i = 0; i < ARRAY_SIZE(amba_ports); i++)
if (amba_ports[i] == uap)
amba_ports[i] = NULL;
+ else if (amba_ports[i])
+ busy = true;
+
+ if (!busy)
+ uart_unregister_driver(&amba_reg);

return 0;
}
@@ -816,23 +836,14 @@ static struct amba_driver pl010_driver = {

static int __init pl010_init(void)
{
- int ret;
-
printk(KERN_INFO "Serial: AMBA driver\n");

- ret = uart_register_driver(&amba_reg);
- if (ret == 0) {
- ret = amba_driver_register(&pl010_driver);
- if (ret)
- uart_unregister_driver(&amba_reg);
- }
- return ret;
+ return amba_driver_register(&pl010_driver);
}

static void __exit pl010_exit(void)
{
amba_driver_unregister(&pl010_driver);
- uart_unregister_driver(&amba_reg);
}

module_init(pl010_init);
--
2.11.0
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