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USB: usbtmc: Add separate USBTMC_IOCTL_GET_SRQ_STB

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This new ioctl only returns the status byte (STB) that was originally
sent by the device due to a service request (SRQ) condition.

This ioctl checks the srq_asserted bit of the associated file
descriptor. If set, the srq_asserted bit is reset and the cached
STB with original SRQ information is returned. Otherwise the ioctl
returns the error code ENOMSG.

This ioctl is useful to support non USBTMC-488 compliant devices.
Time sensitive applications can read the cached STB without incurring
the cost of an urb transaction over the bus.

Tested-by: Jian-Wei Wu <jian-wei_wu@keysight.com>
Reviewed-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://lore.kernel.org/r/20201215155621.9592-4-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dave Penkler 2020-12-15 16:56:20 +01:00 • committed by Greg Kroah-Hartman
parent c9784e23c1
commit d1d9defdc6
2 changed files with 32 additions and 0 deletions
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1
include/uapi/linux/usb/tmc.h
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@ -103,6 +103,7 @@ struct usbtmc_message {
#define USBTMC_IOCTL_AUTO_ABORT _IOW(USBTMC_IOC_NR, 25, __u8)
#define USBTMC_IOCTL_GET_STB _IOR(USBTMC_IOC_NR, 26, __u8)
#define USBTMC_IOCTL_GET_SRQ_STB _IOR(USBTMC_IOC_NR, 27, __u8)
/* Cancel and cleanup asynchronous calls */
#define USBTMC_IOCTL_CANCEL_IO _IO(USBTMC_IOC_NR, 35)