On Fri, Jul 24, 2015 at 08:48:11AM +0200, Petr Tesarik wrote:
> From: Petr Tesarik <ptesarik@xxxxxxx>
>
> Make it possible to read the cp210x part number from userspace by making
> it a sysfs attribute.
>
> Signed-off-by: Petr Tesarik <ptesarik@xxxxxxxx>
All sysfs files need to be documented in Documentation/ABI/
> ---
> drivers/usb/serial/cp210x.c | 21 ++++++++++++++++++++-
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index dbfc722..66de350 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -871,11 +871,24 @@ static void cp210x_break_ctl(struct tty_struct *tty, int break_state)
> cp210x_set_config(port, CP210X_SET_BREAK, &state, 2);
> }
>
> +static ssize_t part_number_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct usb_interface *intf = to_usb_interface(dev);
> + struct usb_serial *serial = usb_get_intfdata(intf);
> + struct cp210x_serial_private *spriv = usb_get_serial_data(serial);
> +
> + return sprintf(buf, "%i\n", spriv->bPartNumber);
> +}
> +
> +static DEVICE_ATTR_RO(part_number);
> +
> static int cp210x_startup(struct usb_serial *serial)
> {
> struct usb_host_interface *cur_altsetting;
> struct cp210x_serial_private *spriv;
> unsigned int partnum;
> + int result;
>
> spriv = kzalloc(sizeof(*spriv), GFP_KERNEL);
> if (!spriv)
> @@ -892,13 +905,19 @@ static int cp210x_startup(struct usb_serial *serial)
> &partnum, 1, USB_CTRL_GET_TIMEOUT);
> spriv->bPartNumber = partnum & 0xFF;
>
> - return 0;
> + result = device_create_file(&serial->interface->dev,
> + &dev_attr_part_number);
You just raced with userspace, it will not properly see this attribute
:(
Please never use device_create_file, use an attribute group assigned to
the tty device. Not the USB interface, that is only for USB interface
"things".
thanks,
greg k-h
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