From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754364Ab3CTXCM (ORCPT ); Wed, 20 Mar 2013 19:02:12 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:55183 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751483Ab3CTXCK (ORCPT ); Wed, 20 Mar 2013 19:02:10 -0400 From: Stephen Warren To: Mark Brown Cc: linux-kernel@vger.kernel.org, Stephen Warren , Laxman Dewangan Subject: [PATCH] regmap: don't corrupt work buffer in _regmap_raw_write() Date: Wed, 20 Mar 2013 17:02:02 -0600 Message-Id: <1363820522-25954-1-git-send-email-swarren@wwwdotorg.org> X-Mailer: git-send-email 1.7.10.4 X-NVConfidentiality: public Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Stephen Warren _regmap_raw_write() contains code to call regcache_write() to write values to the cache. That code calls memcpy() to copy the value data to the start of the work_buf. However, at least when _regmap_raw_write() is called from _regmap_bus_raw_write(), the value data is in the work_buf, and this memcpy() operation may over-write part of that value data, depending on the value of reg_bytes + pad_bytes. At least when using reg_bytes==1 and pad_bytes==0, corruption of the value data does occur. To solve this, remove the memcpy() operation, and modify the subsequent .parse_val() call to parse the original value buffer directly. At least in the case of 8-bit register address and 16-bit values, and writes of single registers at a time, this memcpy-then-parse combination used to cancel each-other out; for a work-buffer containing xx 89 03, the memcpy changed it to 89 03 03, and the parse_val changed it back to 89 89 03, thus leaving the value uncorrupted. This appears completely accidental though. Since commit 8a819ff "regmap: core: Split out in place value parsing", .parse_val only returns the parsed value, and does not modify the buffer, and hence does not (accidentally) undo the corruption caused by memcpy(). This caused bogus values to get written to HW, thus preventing e.g. audio playback on systems with a WM8903 CODEC. This patch fixes that. Cc: Laxman Dewangan Signed-off-by: Stephen Warren --- drivers/base/regmap/regmap.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c index fed91ac..1ab4498 100644 --- a/drivers/base/regmap/regmap.c +++ b/drivers/base/regmap/regmap.c @@ -963,8 +963,7 @@ static int _regmap_raw_write(struct regmap *map, unsigned int reg, unsigned int ival; int val_bytes = map->format.val_bytes; for (i = 0; i < val_len / val_bytes; i++) { - memcpy(map->work_buf, val + (i * val_bytes), val_bytes); - ival = map->format.parse_val(map->work_buf); + ival = map->format.parse_val(val + (i * val_bytes)); ret = regcache_write(map, reg + (i * map->reg_stride), ival); if (ret) { -- 1.7.10.4