USB: serial: pl2303: account for deficits of clones

There are apparently incomplete clones of the HXD type chip in use.
Those return -EPIPE on GET_LINE_REQUEST and BREAK_REQUEST. Avoid
flooding the kernel log with those errors. Detect them during startup
and then use the line_settings cache instead of GET_LINE_REQUEST. Signal
missing break support via -ENOTTY.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
[ johan: fix macro prefix, drop oom error message ]
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index ad41363e3cea5abd09ff24a85e4c670bd5d1de67..010688dd9e49ced5fdf9e5dd808604304b27452b 100644 (file)
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -31,6 +31,7 @@
 #define PL2303_QUIRK_UART_STATE_IDX0           BIT(0)
 #define PL2303_QUIRK_LEGACY                    BIT(1)
 #define PL2303_QUIRK_ENDPOINT_HACK             BIT(2)
+#define PL2303_QUIRK_NO_BREAK_GETLINE          BIT(3)
 
 static const struct usb_device_id id_table[] = {
        { USB_DEVICE(PL2303_VENDOR_ID, PL2303_PRODUCT_ID),
@@ -467,6 +468,25 @@ static int pl2303_detect_type(struct usb_serial *serial)
        return -ENODEV;
 }
 
+static bool pl2303_is_hxd_clone(struct usb_serial *serial)
+{
+       struct usb_device *udev = serial->dev;
+       unsigned char *buf;
+       int ret;
+
+       buf = kmalloc(7, GFP_KERNEL);
+       if (!buf)
+               return false;
+
+       ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
+                             GET_LINE_REQUEST, GET_LINE_REQUEST_TYPE,
+                             0, 0, buf, 7, 100);
+
+       kfree(buf);
+
+       return ret == -EPIPE;
+}
+
 static int pl2303_startup(struct usb_serial *serial)
 {
        struct pl2303_serial_private *spriv;
@@ -489,6 +509,9 @@ static int pl2303_startup(struct usb_serial *serial)
        spriv->quirks = (unsigned long)usb_get_serial_data(serial);
        spriv->quirks |= spriv->type->quirks;
 
+       if (type == TYPE_HXD && pl2303_is_hxd_clone(serial))
+               spriv->quirks |= PL2303_QUIRK_NO_BREAK_GETLINE;
+
        usb_set_serial_data(serial, spriv);
 
        if (type != TYPE_HXN) {
@@ -725,9 +748,18 @@ static void pl2303_encode_baud_rate(struct tty_struct *tty,
 static int pl2303_get_line_request(struct usb_serial_port *port,
                                                        unsigned char buf[7])
 {
-       struct usb_device *udev = port->serial->dev;
+       struct usb_serial *serial = port->serial;
+       struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
+       struct usb_device *udev = serial->dev;
        int ret;
 
+       if (spriv->quirks & PL2303_QUIRK_NO_BREAK_GETLINE) {
+               struct pl2303_private *priv = usb_get_serial_port_data(port);
+
+               memcpy(buf, priv->line_settings, 7);
+               return 0;
+       }
+
        ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
                                GET_LINE_REQUEST, GET_LINE_REQUEST_TYPE,
                                0, 0, buf, 7, 100);
@@ -1064,9 +1096,13 @@ static int pl2303_carrier_raised(struct usb_serial_port *port)
 static int pl2303_set_break(struct usb_serial_port *port, bool enable)
 {
        struct usb_serial *serial = port->serial;
+       struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
        u16 state;
        int result;
 
+       if (spriv->quirks & PL2303_QUIRK_NO_BREAK_GETLINE)
+               return -ENOTTY;
+
        if (enable)
                state = BREAK_ON;
        else