From 19e4ec525b37cdecbdb4f86edaae7f56a67339ee Mon Sep 17 00:00:00 2001 From: Benjamin Tissoires Date: Wed, 30 Apr 2014 17:48:40 -0400 Subject: [PATCH] HID: core: fix computation of the report size The extra seven bits are only required when allocating the report buffer. We can not use those extra bytes for the length of the report in the generic implementation of .request because the device might (will) refuse the set_report command. This has been verified on the Atmel touchpad found on the Samsung Ativ 9 plus, which uses hid-multitouch and HID over I2C. Without this fix, the device refuses to switch to the multitouch mode, and it becomes unresponsive from the user point of view. Actually, this has been discussed during the initial submission of the commit 4fa5a7f76cc7b6ac87f57741edd2b124851d119f, see https://patchwork.kernel.org/patch/3621751/ Unfortunately, I completely forgot about it later. Reported-by: Matthias Bayer Signed-off-by: Benjamin Tissoires Signed-off-by: Jiri Kosina --- drivers/hid/hid-core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 10a2c08..da52279 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1253,7 +1253,8 @@ EXPORT_SYMBOL_GPL(hid_output_report); static int hid_report_len(struct hid_report *report) { - return ((report->size - 1) >> 3) + 1 + (report->id > 0) + 7; + /* equivalent to DIV_ROUND_UP(report->size, 8) + !!(report->id > 0) */ + return ((report->size - 1) >> 3) + 1 + (report->id > 0); } /* @@ -1266,7 +1267,7 @@ u8 *hid_alloc_report_buf(struct hid_report *report, gfp_t flags) * of implement() working on 8 byte chunks */ - int len = hid_report_len(report); + int len = hid_report_len(report) + 7; return kmalloc(len, flags); } -- 2.7.4