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HID: hidraw: Add additional hidraw input/output report ioctls.

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Currently the hidraw module can only read and write feature HID reports on
demand, via dedicated ioctls. Input reports are read from the device through
the read() interface, while output reports are written through the write
interface().

This is insufficient; it is desirable in many situations to be able to read and
write input and output reports through the control interface to cover
additional scenarios:

  - Reading an input report by its report ID, to get initial state
  - Writing an input report, to set initial input state in the device
  - Reading an output report by its report ID, to obtain current state
  - Writing an output report by its report ID, out of band

This patch adds these missing ioctl requests to read and write the remaining
HID report types. Note that not all HID backends will neccesarily support this
(e.g. while the USB link layer supports setting Input reports, others may not).

Also included are documentation and example updates. The current hidraw
documentation states that feature reports read from the device does *not*
include the report ID, however this is not the case and the returned report
will have its report ID prepended by conforming HID devices, as the report data
sent from the device over the control endpoint must be indentical in format to
those sent over the regular transport.

Signed-off-by: Dean Camera <dean@fourwalledcubicle.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Dean Camera 2020-11-26 09:39:57 +11:00 committed by Jiri Kosina
parent 6a0eaf5123
commit f43d3870ca
4 changed files with 73 additions and 4 deletions
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45
Documentation/hid/hidraw.rst
View File

@ -123,8 +123,49 @@ HIDIOCGFEATURE(len):
This ioctl will request a feature report from the device using the control
endpoint. The first byte of the supplied buffer should be set to the report
number of the requested report. For devices which do not use numbered
reports, set the first byte to 0. The report will be returned starting at
the first byte of the buffer (ie: the report number is not returned).
reports, set the first byte to 0. The returned report buffer will contain the
report number in the first byte, followed by the report data read from the
device. For devices which do not use numbered reports, the report data will
begin at the first byte of the returned buffer.
HIDIOCSINPUT(len):
Send an Input Report
This ioctl will send an input report to the device, using the control endpoint.
In most cases, setting an input HID report on a device is meaningless and has
no effect, but some devices may choose to use this to set or reset an initial
state of a report. The format of the buffer issued with this report is identical
to that of HIDIOCSFEATURE.
HIDIOCGINPUT(len):
Get an Input Report
This ioctl will request an input report from the device using the control
endpoint. This is slower on most devices where a dedicated In endpoint exists
for regular input reports, but allows the host to request the value of a
specific report number. Typically, this is used to request the initial states of
an input report of a device, before an application listens for normal reports via
the regular device read() interface. The format of the buffer issued with this report
is identical to that of HIDIOCGFEATURE.
HIDIOCSOUTPUT(len):
Send an Output Report
This ioctl will send an output report to the device, using the control endpoint.
This is slower on most devices where a dedicated Out endpoint exists for regular
output reports, but is added for completeness. Typically, this is used to set
the initial states of an output report of a device, before an application sends
updates via the regular device write() interface. The format of the buffer issued
with this report is identical to that of HIDIOCSFEATURE.
HIDIOCGOUTPUT(len):
Get an Output Report
This ioctl will request an output report from the device using the control
endpoint. Typically, this is used to retrive the initial state of
an output report of a device, before an application updates it as necessary either
via a HIDIOCSOUTPUT request, or the regular device write() interface. The format
of the buffer issued with this report is identical to that of HIDIOCGFEATURE.
Example
-------

24
drivers/hid/hidraw.c
View File

@ -170,7 +170,7 @@ static ssize_t hidraw_write(struct file *file, const char __user *buffer, size_t
/*
* This function performs a Get_Report transfer over the control endpoint
* per section 7.2.1 of the HID specification, version 1.1. The first byte
* of buffer is the report number to request, or 0x0 if the defice does not
* of buffer is the report number to request, or 0x0 if the device does not
* use numbered reports. The report_type parameter can be HID_FEATURE_REPORT
* or HID_INPUT_REPORT.
*/
@ -428,6 +428,28 @@ static long hidraw_ioctl(struct file *file, unsigned int cmd,
break;
}
if (_IOC_NR(cmd) == _IOC_NR(HIDIOCSINPUT(0))) {
int len = _IOC_SIZE(cmd);
ret = hidraw_send_report(file, user_arg, len, HID_INPUT_REPORT);
break;
}
if (_IOC_NR(cmd) == _IOC_NR(HIDIOCGINPUT(0))) {
int len = _IOC_SIZE(cmd);
ret = hidraw_get_report(file, user_arg, len, HID_INPUT_REPORT);
break;
}
if (_IOC_NR(cmd) == _IOC_NR(HIDIOCSOUTPUT(0))) {
int len = _IOC_SIZE(cmd);
ret = hidraw_send_report(file, user_arg, len, HID_OUTPUT_REPORT);
break;
}
if (_IOC_NR(cmd) == _IOC_NR(HIDIOCGOUTPUT(0))) {
int len = _IOC_SIZE(cmd);
ret = hidraw_get_report(file, user_arg, len, HID_OUTPUT_REPORT);
break;
}
/* Begin Read-only ioctls. */
if (_IOC_DIR(cmd) != _IOC_READ) {
ret = -EINVAL;

6
include/uapi/linux/hidraw.h
View File

@ -40,6 +40,12 @@ struct hidraw_devinfo {
#define HIDIOCSFEATURE(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x06, len)
#define HIDIOCGFEATURE(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x07, len)
#define HIDIOCGRAWUNIQ(len) _IOC(_IOC_READ, 'H', 0x08, len)
/* The first byte of SINPUT and GINPUT is the report number */
#define HIDIOCSINPUT(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x09, len)
#define HIDIOCGINPUT(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x0A, len)
/* The first byte of SOUTPUT and GOUTPUT is the report number */
#define HIDIOCSOUTPUT(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x0B, len)
#define HIDIOCGOUTPUT(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x0C, len)
#define HIDRAW_FIRST_MINOR 0
#define HIDRAW_MAX_DEVICES 64

2
samples/hidraw/hid-example.c
View File

@ -128,7 +128,7 @@ int main(int argc, char **argv)
perror("HIDIOCGFEATURE");
} else {
printf("ioctl HIDIOCGFEATURE returned: %d\n", res);
printf("Report data (not containing the report number):\n\t");
printf("Report data:\n\t");
for (i = 0; i < res; i++)
printf("%hhx ", buf[i]);
puts("\n");