From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753998AbdEIMY0 (ORCPT ); Tue, 9 May 2017 08:24:26 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:34444 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752552AbdEIMYY (ORCPT ); Tue, 9 May 2017 08:24:24 -0400 From: Seraphime Kirkovski To: linux-kernel@vger.kernel.org Cc: linux-spi@vger.kernel.org, broonie@kernel.org, Seraphime Kirkovski Subject: [PATCH 1/2] spi: spidev: introduce SPI_IOC_WR_DEFAULT_MAX_SPEED_HZ command Date: Tue, 9 May 2017 14:24:00 +0200 Message-Id: <20170509122401.2561-2-kirkseraph@gmail.com> X-Mailer: git-send-email 2.13.0.rc1 In-Reply-To: <20170509122401.2561-1-kirkseraph@gmail.com> References: <20170509122401.2561-1-kirkseraph@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Historically SPI_IOC_WR_MAX_SPEED_HZ was changing the ->max_speed_hz field of the underlying struct spi_dev, which made the effects last way after releasing one particular /dev/spidev* fd. This changed in 9169051617df7 ("spi: spidev: Don't mangle max_speed_hz in underlying spi device") or 7 years after the introduction of SPI_IOC_WR_MAX_SPEED_HZ ! In the mean time there were userspace tools developped with the assumptions that the effects of this particular command are system-wide. [1] is a suite of two small programs for reading, writing and configuring SPI interfaces. The `spi-config -s` part was working good in our setup with old 3.x kernels. We discovered this "regression" when we tried to port our workflow to newer kernels. I think, this change is necessary, on the one hand, because there are still a lot of longterm[2] supported kernels out there, whose users may be relying on SPI_IOC_WR_MAX_SPEED being system-wide and, on the other hand, this same command has been exhibiting a different behaviour for 3 years now, so its users may break, if 9169051617df7 is reverted in one way or another. The semantics of the proposed command are the same as the old SPI_IOC_WR_MAX_SPEED_HZ. [1] https://github.com/cpb-/spi-tools [2] A quick check on kernel.org shows that all 3.x with longterm support have not applied 9169051617df7 Signed-off-by: Seraphime Kirkovski (Haapie) --- drivers/spi/spidev.c | 8 ++++++-- include/uapi/linux/spi/spidev.h | 4 +++- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index 9a2a79a871ba..18d310db90ab 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -474,6 +474,7 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) dev_dbg(&spi->dev, "%d bits per word\n", tmp); } break; + case SPI_IOC_WR_DEFAULT_MAX_SPEED_HZ: case SPI_IOC_WR_MAX_SPEED_HZ: retval = __get_user(tmp, (__u32 __user *)arg); if (retval == 0) { @@ -483,9 +484,12 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) retval = spi_setup(spi); if (retval >= 0) spidev->speed_hz = tmp; - else + else { dev_dbg(&spi->dev, "%d Hz (max)\n", tmp); - spi->max_speed_hz = save; + spi->max_speed_hz = save; + } + if (cmd != SPI_IOC_WR_DEFAULT_MAX_SPEED_HZ) + spi->max_speed_hz = save; } break; diff --git a/include/uapi/linux/spi/spidev.h b/include/uapi/linux/spi/spidev.h index dd5f21e75805..91ed22154bc0 100644 --- a/include/uapi/linux/spi/spidev.h +++ b/include/uapi/linux/spi/spidev.h @@ -128,7 +128,7 @@ struct spi_ioc_transfer { #define SPI_IOC_RD_BITS_PER_WORD _IOR(SPI_IOC_MAGIC, 3, __u8) #define SPI_IOC_WR_BITS_PER_WORD _IOW(SPI_IOC_MAGIC, 3, __u8) -/* Read / Write SPI device default max speed hz */ +/* Read / Write SPI device max speed hz */ #define SPI_IOC_RD_MAX_SPEED_HZ _IOR(SPI_IOC_MAGIC, 4, __u32) #define SPI_IOC_WR_MAX_SPEED_HZ _IOW(SPI_IOC_MAGIC, 4, __u32) @@ -136,6 +136,8 @@ struct spi_ioc_transfer { #define SPI_IOC_RD_MODE32 _IOR(SPI_IOC_MAGIC, 5, __u32) #define SPI_IOC_WR_MODE32 _IOW(SPI_IOC_MAGIC, 5, __u32) +/* Write SPI device default max speed hz */ +#define SPI_IOC_WR_DEFAULT_MAX_SPEED_HZ _IOW(SPI_IOC_MAGIC, 6, __u32) #endif /* SPIDEV_H */ -- 2.13.0.rc1