Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755743Ab1CQVmf (ORCPT ); Thu, 17 Mar 2011 17:42:35 -0400 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:36823 "EHLO opensource2.wolfsonmicro.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755662Ab1CQVmd (ORCPT ); Thu, 17 Mar 2011 17:42:33 -0400 From: Mark Brown To: Samuel Ortiz Cc: linux-kernel@vger.kernel.org, patches@opensource.wolfsonmicro.com, Mark Brown Subject: [PATCH 1/3] mfd: Avoid copying data in WM8994 I2C write Date: Thu, 17 Mar 2011 21:42:28 +0000 Message-Id: <1300398150-11834-1-git-send-email-broonie@opensource.wolfsonmicro.com> X-Mailer: git-send-email 1.7.4.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1764 Lines: 60 As well as providing a trivial performance optimisation this also avoids allocating a copy of the message on the stack which is beneficial when doing large transfers. Signed-off-by: Mark Brown --- drivers/mfd/wm8994-core.c | 22 +++++++++++++--------- 1 files changed, 13 insertions(+), 9 deletions(-) diff --git a/drivers/mfd/wm8994-core.c b/drivers/mfd/wm8994-core.c index 749c31d..ce93796 100644 --- a/drivers/mfd/wm8994-core.c +++ b/drivers/mfd/wm8994-core.c @@ -580,25 +580,29 @@ static int wm8994_i2c_read_device(struct wm8994 *wm8994, unsigned short reg, return 0; } -/* Currently we allocate the write buffer on the stack; this is OK for - * small writes - if we need to do large writes this will need to be - * revised. - */ static int wm8994_i2c_write_device(struct wm8994 *wm8994, unsigned short reg, int bytes, void *src) { struct i2c_client *i2c = wm8994->control_data; - unsigned char msg[bytes + 2]; + struct i2c_msg xfer[2]; int ret; reg = cpu_to_be16(reg); - memcpy(&msg[0], ®, 2); - memcpy(&msg[2], src, bytes); - ret = i2c_master_send(i2c, msg, bytes + 2); + xfer[0].addr = i2c->addr; + xfer[0].flags = 0; + xfer[0].len = 2; + xfer[0].buf = (char *)® + + xfer[1].addr = i2c->addr; + xfer[1].flags = I2C_M_NOSTART; + xfer[1].len = bytes; + xfer[1].buf = (char *)src; + + ret = i2c_transfer(i2c->adapter, xfer, 2); if (ret < 0) return ret; - if (ret < bytes + 2) + if (ret != 2) return -EIO; return 0; -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/