On 6/7/23 02:33, Rodolfo Giometti wrote:
On 05/06/23 22:31, Charlie Johnston wrote:
For consistency with what ptp uses for minors, this
change sets PPS_MAX_SOURCES to MINORMASK + 1.
The PPS_MAX_SOURCES value is currently set to 16. In
some cases this was not sufficient for a system. For
example, a system with multiple (4+) PCIe cards each
with 4 PTP-capable ethernet interfaces could run out
of the available PPS major:minors if each interface
registers a PPS source.
Signed-off-by: Charlie Johnston <charlie.johnston@xxxxxx>
---
include/uapi/linux/pps.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/uapi/linux/pps.h b/include/uapi/linux/pps.h
index 009ebcd8ced5..85f472330da8 100644
--- a/include/uapi/linux/pps.h
+++ b/include/uapi/linux/pps.h
@@ -26,7 +26,7 @@
#include <linux/types.h>
#define PPS_VERSION "5.3.6"
-#define PPS_MAX_SOURCES 16 /* should be enough... */
+#define PPS_MAX_SOURCES (MINORMASK + 1)
/* Implementation note: the logical states ``assert'' and ``clear''
* are implemented in terms of the chip register, i.e. ``assert''
I have just one question: are you sure that it's safe to call idr_alloc(..., 0, (MINORMASK + 1), ...)?
Ciao,
Rodolfo
Thanks for taking a look!
My understanding is that idr_alloc(..., start, end, ...) can take any end value up to INT_MAX. It also handles any values <= 0 by treating them as equal to INT_MAX + 1 since the end value is non-inclusive. I can't think of any reason using MINORMASK + 1 here would be an issue since it's much less than the maximum value idr_alloc() allows.
A number of drivers (e.g. ptp) just explicitly use a start and end value of 0, but I don't think that change would fit here.