From: "Song, Hongyan" <hongyan.song@xxxxxxxxx>
The maximum globale report size has changed from 32->...->96->128 in
the past years.
With the development usage of HID, the report_size max value 128 cannot
satisfy all requirements.
There are applications need to expose intrinsic metadata to camera
stabilizing applications such as 3DFE application. 3DFE intrinsic is
designed to express environmental information about sensor that may
dynamically change while the sensor is running (such data include
noise spectral density, bias standard deviation …)
A sensor data field is SENSOR_VALUE_PAIR that consists of a PROPERTYKEY
and PROPVARIANT pair. It need to report a unique PROPERTYKEY for each
data field.
Take “Noise Spectral Density” as an example, it report count will be
defined as below:
"Size of Property key GUID(16 Byte) + property key index(4 Byte) +
size of Noise Spectral Density value(4 Byte)"
In this case, the data report max is totally 192(24Byte), which is larger
than 128, while max size 128 blocked it as illegal length. So increase the
report size to satisfy it and more demands in the future.
Signed-off-by: Song Hongyan <hongyan.song@xxxxxxxxx>
---
V2: update the comments
drivers/hid/hid-core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 3942ee6..d9c1d12 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -396,7 +396,7 @@ static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)
case HID_GLOBAL_ITEM_TAG_REPORT_SIZE:
parser->global.report_size = item_udata(item);
- if (parser->global.report_size > 128) {
+ if (parser->global.report_size > 256) {
hid_err(parser->device, "invalid report_size %d\n",
parser->global.report_size);
return -1;
--
2.7.4
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