Re: [PATCH igt v3] lib: Add simple sysfs accessors

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, May 26, 2016 at 05:19:35PM +0100, Chris Wilson wrote:
> igt_sysfs_set() for setting an attribute via sysfs, igt_sysfs_get() for
> reading.
> 
> v2: Lots of little bugs in igt_sysfs_get()
> v3: Pass device to open, stop assuming Intel rules.
> v4: Test opening and reading!
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  lib/Makefile.sources |   2 +
>  lib/igt_sysfs.c      | 205 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/igt_sysfs.h      |  34 +++++++++
>  3 files changed, 241 insertions(+)
>  create mode 100644 lib/igt_sysfs.c
>  create mode 100644 lib/igt_sysfs.h
> 
> diff --git a/lib/Makefile.sources b/lib/Makefile.sources
> index 1316fd2..f50ff4d 100644
> --- a/lib/Makefile.sources
> +++ b/lib/Makefile.sources
> @@ -16,6 +16,8 @@ libintel_tools_la_SOURCES = 	\
>  	igt_gt.h		\
>  	igt_stats.c		\
>  	igt_stats.h		\
> +	igt_sysfs.c		\
> +	igt_sysfs.h		\
>  	instdone.c		\
>  	instdone.h		\
>  	intel_batchbuffer.c	\
> diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
> new file mode 100644
> index 0000000..e9dba0a
> --- /dev/null
> +++ b/lib/igt_sysfs.c
> @@ -0,0 +1,205 @@
> +/*
> + * Copyright © 2016 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + *
> + */
> +
> +#include <inttypes.h>
> +#include <sys/stat.h>
> +#include <sys/mount.h>
> +#include <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <limits.h>
> +#include <string.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <i915_drm.h>
> +
> +#include "igt_sysfs.h"
> +
> +static int readN(int fd, char *buf, int len)
> +{
> +	int total = 0;
> +	do {
> +		int ret = read(fd, buf + total, len - total);
> +		if (ret < 0 && (errno == EINTR || errno == EAGAIN))
> +			continue;
> +
> +		if (ret <= 0)
> +			return total ?: ret;
> +
> +		total += ret;
> +	} while (1);
> +}
> +
> +static int writeN(int fd, const char *buf, int len)
> +{
> +	int total = 0;
> +	do {
> +		int ret = write(fd, buf + total, len - total);
> +		if (ret < 0 && (errno == EINTR || errno == EAGAIN))
> +			continue;
> +
> +		if (ret <= 0)
> +			return total ?: ret;
> +
> +		total += ret;
> +	} while (1);
> +}
> +
> +/**
> + * igt_sysfs_open:
> + * @device: fd of the device (or -1 to default to Intel)
> + *
> + * This opens the sysfs directory corresponding to device for use
> + * with igt_sysfs_set() and igt_sysfs_get().
> + *
> + * Returns:
> + * The directory fd, or -1 on failure.
> + */
> +int igt_sysfs_open(int fd, int *idx)
> +{
> +	char device[80];
> +	char path[80];
> +	struct stat st;
> +
> +	device[0] = '\0';
> +	if (fd != -1) {
> +		if (fstat(fd, &st) || !S_ISCHR(st.st_mode))
> +			return -1;
> +
> +		sprintf(device, "%d:%d", major(st.st_rdev), minor(st.st_rdev));
> +	}
> +
> +	for (int n = 0; n < 16; n++) {
> +		int len = sprintf(path, "/sys/class/drm/card%d", n);
> +		if (device[0]) {
> +			char tmp[80];
> +			int ret;
> +
> +			sprintf(path + len, "/dev");
> +			fd = open(path, O_RDONLY);
> +			if (fd == -1)
> +				continue;
> +
> +			ret = read(fd, tmp, sizeof(tmp-1));
> +			if (ret < 0)
> +				ret = 0;
> +			tmp[ret] = '\0';
> +			while (ret > 0 && tmp[ret-1] == '\n')
> +				tmp[--ret] = '\0';
> +			close(fd);
> +
> +			if (strcmp(tmp, device))
> +				continue;

fscanf?

> +		} else {
> +			/* Bleh. Search for intel */
> +			sprintf(path + len, "/error");
> +			if (stat(path, &st))
> +				continue;
> +		}
> +
> +		path[len] = '\0';
> +		if (idx)
> +			*idx = n;
> +		return open(path, O_RDONLY);
> +	}
> +
> +	return -1;
> +}
> +
> +/**
> + * igt_sysfs_set:
> + * @dir: directory for the device from igt_sysfs_open()
> + * @attr: name of the sysfs node to open
> + * @value: the string to write
> + *
> + * This writes the value to the sysfs file.
> + *
> + * Returns:
> + * True on success, false on failure.
> + */
> +bool igt_sysfs_set(int dir, const char *attr, const char *value)
> +{
> +	int fd, len, ret;
> +
> +	fd = openat(dir, attr, O_WRONLY);
> +	if (fd < 0)
> +		return false;
> +
> +	len = strlen(value);
> +	ret = writeN(fd, value, len);
> +	close(fd);
> +
> +	return len == ret;
> +}
> +
> +/**
> + * igt_sysfs_get:
> + * @dir: directory for the device from igt_sysfs_open()
> + * @attr: name of the sysfs node to open
> + *
> + * This reads the value from the sysfs file.
> + *
> + * Returns:
> + * A nul-terminated string, must be freed by caller after use, or NULL
> + * on failure.
> + */
> +char *igt_sysfs_get(int dir, const char *attr)
> +{
> +	char *buf;
> +	int len, offset, rem;
> +	int ret, fd;
> +
> +	fd = openat(dir, attr, O_RDONLY);
> +	if (fd < 0)
> +		return NULL;
> +
> +	offset = 0;
> +	len = 64;
> +	rem = len - offset - 1;
> +	buf = malloc(len);
> +	if (!buf)
> +		goto out;
> +
> +	while ((ret = readN(fd, buf + offset, rem)) == rem) {
> +		char *newbuf;
> +
> +		newbuf = realloc(buf, 2*len);
> +		if (!newbuf)
> +			break;
> +
> +		len *= 2;
> +		offset += ret;
> +		rem = len - offset - 1;
> +	}
> +
> +	if (ret != -1)
> +		offset += ret;
> +	buf[offset] = '\0';
> +	while (offset > 0 && buf[offset-1] == '\n')
> +		buf[--offset] = '\0';
> +
> +out:
> +	close(fd);
> +	return buf;
> +}
> diff --git a/lib/igt_sysfs.h b/lib/igt_sysfs.h
> new file mode 100644
> index 0000000..5c49f64
> --- /dev/null
> +++ b/lib/igt_sysfs.h
> @@ -0,0 +1,34 @@
> +/*
> + * Copyright © 2016 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + *
> + */
> +
> +#ifndef __IGT_SYSFS_H__
> +#define __IGT_SYSFS_H__
> +
> +#include <stdbool.h>
> +
> +int igt_sysfs_open(int device, int *idx);
> +bool igt_sysfs_set(int dir, const char *attr, const char *value);
> +char *igt_sysfs_get(int dir, const char *attr);
> +
> +#endif /* __IGT_SYSFS_H__ */
> -- 
> 2.8.1
> 
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-- 
Ville Syrjälä
Intel OTC
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