selftests/remoteproc: Add selftest suite for sysfs interface

tools/testing/selftests/Makefile

@@ -99,6 +99,7 @@ TARGETS += pstore
 TARGETS += ptrace
 TARGETS += openat2
 TARGETS += rdma
+TARGETS += remoteproc
 TARGETS += resctrl
 TARGETS += riscv
 TARGETS += rlimits

tools/testing/selftests/remoteproc/Makefile

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS += -Wall -O2
+CFLAGS += -Wno-format-truncation
+CFLAGS += $(KHDR_INCLUDES)
+
+TEST_GEN_PROGS := remoteproc_sysfs
+
+include ../lib.mk

tools/testing/selftests/remoteproc/config

@@ -0,0 +1 @@
+CONFIG_REMOTEPROC=y

tools/testing/selftests/remoteproc/remoteproc_helpers.h

@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Helpers for remoteproc selftests: device enumeration and sysfs I/O.
+ */
+#ifndef REMOTEPROC_HELPERS_H
+#define REMOTEPROC_HELPERS_H
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#define RPROC_SYSFS_CLASS	"/sys/class/remoteproc"
+/* Large enough for any full sysfs path including d_name (up to 255). */
+#define RPROC_PATH_MAX		512
+#define RPROC_ATTR_BUF_MAX	32
+#define RPROC_MAX_DEVS		32
+
+/*
+ * Scan /sys/class/remoteproc/ and fill @devs with the full sysfs path of
+ * each remoteprocN entry (e.g. "/sys/class/remoteproc/remoteproc0").
+ * Returns the number of devices found, or 0 if none.
+ */
+static inline int rproc_find_devices(char devs[][RPROC_PATH_MAX], int max)
+{
+	struct dirent *entry;
+	DIR *dir;
+	int count = 0;
+
+	dir = opendir(RPROC_SYSFS_CLASS);
+	if (!dir)
+		return 0;
+
+	while ((entry = readdir(dir)) && count < max) {
+		if (strncmp(entry->d_name, "remoteproc", 10) != 0)
+			continue;
+		snprintf(devs[count], RPROC_PATH_MAX, "%s/%s",
+			 RPROC_SYSFS_CLASS, entry->d_name);
+		count++;
+	}
+
+	closedir(dir);
+	return count;
+}
+
+/*
+ * Read sysfs attribute @attr of device at sysfs path @dev into @buf.
+ * Strips trailing newline. Returns 0 on success, -errno on failure.
+ */
+static inline int rproc_sysfs_read(const char *dev, const char *attr,
+				   char *buf, size_t len)
+{
+	char path[RPROC_PATH_MAX];
+	ssize_t n;
+	int fd;
+
+	snprintf(path, sizeof(path), "%s/%s", dev, attr);
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		return -errno;
+
+	n = read(fd, buf, len - 1);
+	close(fd);
+	if (n < 0)
+		return -errno;
+
+	buf[n] = '\0';
+	if (n > 0 && buf[n - 1] == '\n')
+		buf[n - 1] = '\0';
+
+	return 0;
+}
+
+/*
+ * Write @val to sysfs attribute @attr of device at sysfs path @dev.
+ * Returns 0 on success, -errno on failure.
+ */
+static inline int rproc_sysfs_write(const char *dev, const char *attr,
+				    const char *val)
+{
+	char path[RPROC_PATH_MAX];
+	ssize_t n;
+	int fd;
+
+	snprintf(path, sizeof(path), "%s/%s", dev, attr);
+	fd = open(path, O_WRONLY);
+	if (fd < 0)
+		return -errno;
+
+	n = write(fd, val, strlen(val));
+	close(fd);
+	if (n < 0)
+		return -errno;
+
+	return 0;
+}
+
+#endif /* REMOTEPROC_HELPERS_H */