subr_bus: introduce device_set_descf() and modify allocation logic

device_set_descf() is a printf-like version of device_set_desc().

Allocation code has been transferred from device_set_desc_internal() to
device_set_desc_copy() and device_set_descf() to avoid complicating
device_set_desc_internal(). The "copy" argument in
device_set_desc_internal() has been replaced with a flag which is set
when the description string has been allocated with M_BUS.

Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Reviewed by:	imp, markj
Differential Revision:	https://reviews.freebsd.org/D43370

Author: christosmarg

share/man/man9/Makefile

@@ -1012,6 +1012,7 @@ MLINKS+=device_get_sysctl.9 device_get_sysctl_ctx.9 \
 MLINKS+=device_quiet.9 device_is_quiet.9 \
 	device_quiet.9 device_verbose.9
 MLINKS+=device_set_desc.9 device_get_desc.9 \
+	device_set_desc.9 device_set_descf.9 \
 	device_set_desc.9 device_set_desc_copy.9
 MLINKS+=device_set_flags.9 device_get_flags.9
 MLINKS+=devstat.9 devicestat.9 \

share/man/man9/device_set_desc.9

@@ -26,11 +26,12 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd June 16, 1998
+.Dd January 9, 2024
 .Dt DEVICE_SET_DESC 9
 .Os
 .Sh NAME
 .Nm device_set_desc ,
+.Nm device_set_descf ,
 .Nm device_set_desc_copy ,
 .Nm device_get_desc
 .Nd access the description of a device
@@ -40,6 +41,8 @@
 .Ft void
 .Fn device_set_desc "device_t dev" "const char *desc"
 .Ft void
+.Fn device_set_descf "device_t dev" "const char *fmt" "..."
+.Ft void
 .Fn device_set_desc_copy "device_t dev" "const char *desc"
 .Ft const char *
 .Fn device_get_desc "device_t dev"
@@ -54,6 +57,9 @@ is used to set the description if the string passed is a temporary
 buffer which will be overwritten.
 In this case, the system will copy
 the string, otherwise the pointer passed will be used directly.
+.Fn device_set_descf
+is a printf-like version of
+.Fn device_set_desc .
 .Sh SEE ALSO
 .Xr device 9
 .Sh AUTHORS

sys/kern/subr_bus.c

@@ -1997,24 +1997,17 @@ device_log(device_t dev, int pri, const char * fmt, ...)
  * @internal
  */
 static void
-device_set_desc_internal(device_t dev, const char* desc, int copy)
+device_set_desc_internal(device_t dev, const char *desc, bool allocated)
 {
 	if (dev->desc && (dev->flags & DF_DESCMALLOCED)) {
 		free(dev->desc, M_BUS);
 		dev->flags &= ~DF_DESCMALLOCED;
 		dev->desc = NULL;
 	}
 
-	if (copy && desc) {
-		dev->desc = malloc(strlen(desc) + 1, M_BUS, M_NOWAIT);
-		if (dev->desc) {
-			strcpy(dev->desc, desc);
-			dev->flags |= DF_DESCMALLOCED;
-		}
-	} else {
-		/* Avoid a -Wcast-qual warning */
-		dev->desc = (char *)(uintptr_t) desc;
-	}
+	if (allocated && desc)
+		dev->flags |= DF_DESCMALLOCED;
+	dev->desc = __DECONST(char *, desc);
 
 	bus_data_generation_update();
 }
@@ -2027,9 +2020,26 @@ device_set_desc_internal(device_t dev, const char* desc, int copy)
  * call to device_set_desc() or device_set_desc_copy()).
  */
 void
-device_set_desc(device_t dev, const char* desc)
+device_set_desc(device_t dev, const char *desc)
+{
+	device_set_desc_internal(dev, desc, false);
+}
+
+/**
+ * @brief Set the device's description
+ *
+ * A printf-like version of device_set_desc().
+ */
+void
+device_set_descf(device_t dev, const char *fmt, ...)
 {
-	device_set_desc_internal(dev, desc, FALSE);
+	va_list ap;
+	char *buf = NULL;
+
+	va_start(ap, fmt);
+	vasprintf(&buf, M_BUS, fmt, ap);
+	va_end(ap);
+	device_set_desc_internal(dev, buf, true);
 }
 
 /**
@@ -2039,9 +2049,12 @@ device_set_desc(device_t dev, const char* desc)
  * the device description is generated, (e.g. with sprintf()).
  */
 void
-device_set_desc_copy(device_t dev, const char* desc)
+device_set_desc_copy(device_t dev, const char *desc)
 {
-	device_set_desc_internal(dev, desc, TRUE);
+	char *buf;
+
+	buf = strdup_flags(desc, M_BUS, M_NOWAIT);
+	device_set_desc_internal(dev, buf, true);
 }
 
 /**

sys/sys/bus.h

@@ -660,6 +660,7 @@ int	device_quiesce(device_t dev);
 void	device_quiet(device_t dev);
 void	device_quiet_children(device_t dev);
 void	device_set_desc(device_t dev, const char* desc);
+void	device_set_descf(device_t dev, const char* fmt, ...) __printflike(2, 3);
 void	device_set_desc_copy(device_t dev, const char* desc);
 int	device_set_devclass(device_t dev, const char *classname);
 int	device_set_devclass_fixed(device_t dev, const char *classname);