Re: [PATCH v6 1/5] Implement an ioctl to support the USMTMC-USB488 READ_STATUS_BYTE operation.

[Greg KH]

On Sun, Nov 29, 2015 at 01:28:49PM +0100, Dave Penkler wrote:
> Background:
> When performing a read on an instrument that is executing a function
> that runs longer than the USB timeout the instrument may hang and
> require a device reset to recover. The READ_STATUS_BYTE operation
> always returns even when the instrument is busy permitting to poll
> for the appropriate condition. This capability is referred to in
> instrument application notes on synchronizing acquisitions for other
> platforms.
> 
> Signed-off-by: Dave Penkler <dpenkler@xxxxxxxxx>
> ---
>  drivers/usb/class/usbtmc.c   | 200 +++++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/usb/tmc.h |   2 +
>  2 files changed, 202 insertions(+)
> 
> diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
> index 7a11a82..89456df9 100644
> --- a/drivers/usb/class/usbtmc.c
> +++ b/drivers/usb/class/usbtmc.c
> @@ -87,6 +87,19 @@ struct usbtmc_device_data {
>  	u8 bTag_last_write;	/* needed for abort */
>  	u8 bTag_last_read;	/* needed for abort */
>  
> +	/* data for interrupt in endpoint handling */
> +	u8             bNotify1;
> +	u8             bNotify2;
> +	u16            ifnum;
> +	u8             iin_bTag;
> +	u8            *iin_buffer;
> +	atomic_t       iin_data_valid;
> +	unsigned int   iin_ep;
> +	int            iin_ep_present;
> +	int            iin_interval;
> +	struct urb    *iin_urb;
> +	u16            iin_wMaxPacketSize;
> +
>  	u8 rigol_quirk;
>  
>  	/* attributes from the USB TMC spec for this device */
> @@ -99,6 +112,7 @@ struct usbtmc_device_data {
>  	struct usbtmc_dev_capabilities	capabilities;
>  	struct kref kref;
>  	struct mutex io_mutex;	/* only one i/o function running at a time */
> +	wait_queue_head_t waitq;
>  };
>  #define to_usbtmc_data(d) container_of(d, struct usbtmc_device_data, kref)
>  
> @@ -373,6 +387,83 @@ exit:
>  	return rv;
>  }
>  
> +static int usbtmc488_ioctl_read_stb(struct usbtmc_device_data *data,
> +				unsigned long arg)

Minor nit, make arg be a "void __user *" here, then there is no need to
cast it later on.

thanks,

greg k-h