remoteproc: Add a sysfs interface for name

[ Upstream commit 6ed756aa0148a5ad0dbdced6f14f22e2f5748d35 ]

This patch adds a sysfs interface that provides the name of the
remote processor to userspace. This allows the userspace to identify
a remote processor as the remoteproc devices themselves are created
based on probe order and can change from one boot to another or
at runtime.

The name is made available in debugfs originally, and is being
retained for now. This can be cleaned up after couple of releases
once users get familiar with the new interface.

[s-anna@ti.com: cherry-pick commit '6ed756aa0148' from v5.4]
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Documentation/ABI/testing/sysfs-class-remoteproc

@@ -48,3 +48,13 @@ Description:	Remote processor state
 
 		Writing "stop" will attempt to halt the remote processor and
 		return it to the "offline" state.
+
+What:		/sys/class/remoteproc/.../name
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Suman Anna <s-anna@ti.com>
+Description:	Remote processor name
+
+		Reports the name of the remote processor. This can be used by
+		userspace in exactly identifying a remote processor and ease
+		up the usage in modifying the 'firmware' or 'state' files.

drivers/remoteproc/remoteproc_sysfs.c

@@ -115,9 +115,20 @@ static ssize_t state_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(state);
 
+/* Expose the name of the remote processor via sysfs */
+static ssize_t name_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct rproc *rproc = to_rproc(dev);
+
+	return sprintf(buf, "%s\n", rproc->name);
+}
+static DEVICE_ATTR_RO(name);
+
 static struct attribute *rproc_attrs[] = {
 	&dev_attr_firmware.attr,
 	&dev_attr_state.attr,
+	&dev_attr_name.attr,
 	NULL
 };