From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.5 required=3.0 tests=BAYES_00,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C6D5C636C8 for ; Sun, 18 Jul 2021 14:53:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 04A1A61183 for ; Sun, 18 Jul 2021 14:53:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233869AbhGRO4g (ORCPT ); Sun, 18 Jul 2021 10:56:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:54056 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232895AbhGRO4f (ORCPT ); Sun, 18 Jul 2021 10:56:35 -0400 Received: from jic23-huawei (cpc108967-cmbg20-2-0-cust86.5-4.cable.virginm.net [81.101.6.87]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 53069610A5; Sun, 18 Jul 2021 14:53:35 +0000 (UTC) Date: Sun, 18 Jul 2021 15:55:59 +0100 From: Jonathan Cameron To: linux-iio@vger.kernel.org, Andy Shevchenko , Nuno Sa Cc: Linus Walleij , Jan Kiszka , Jonathan Cameron Subject: Re: [PATCH v2 0/4] IIO: Alignment fixes part 4 - bounce buffers for the hard cases. Message-ID: <20210718155559.4eb7bf7a@jic23-huawei> In-Reply-To: <20210613151039.569883-1-jic23@kernel.org> References: <20210613151039.569883-1-jic23@kernel.org> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Sun, 13 Jun 2021 16:10:35 +0100 Jonathan Cameron wrote: > From: Jonathan Cameron Hi All, If anyone has time to take a look at this, particularly the first patch which does the interesting stuff and patch 3 which I don't think has had any review yet that would be great. Thanks, Jonathan > > Thanks to Andy and Nuno for reviews. > > Chances since V1/RFC: > * Renamed the function to iio_push_to_buffer_with_ts_unaligned() > * Fixed the various bugs people pointed out. > * Used more standard realloc handling to be more 'obviously' correct. > * Added some additional comments on the sizing of the copy to explain why > it is a conservative estimate and may copy more than strictly necessary. > > A few things we discussed I didn't do (for now)... > > I decided against adding explicit bounce buffer allocation calls for now, > though I'm open to doing that in future if we find doing the somewhat hidden > realloc to be a problem. > > I haven't computed a more precise data_sz as I don't thing the benefits > of a more precise copy or not passing the size, make it worth the slight > reduction in complexity for the callers. Again, open to revisiting this > in future! > > I tested it by hacking the dummy driver to shift it's data by one > byte and call iio_push_to_buffers_with_ts_unaligned(). > > Strictly a hack. I definitely don't want to move this driver over to this > new interface as it might encourage inappropriate use. > > diff --git a/drivers/iio/dummy/iio_simple_dummy_buffer.c b/drivers/iio/dummy/iio_simple_dummy_buffer.c > index 59aa60d4ca37..b47af7df8efc 100644 > --- a/drivers/iio/dummy/iio_simple_dummy_buffer.c > +++ b/drivers/iio/dummy/iio_simple_dummy_buffer.c > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > > #include "iio_simple_dummy.h" > > @@ -78,12 +79,13 @@ static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p) > j = find_next_bit(indio_dev->active_scan_mask, > indio_dev->masklength, j); > /* random access read from the 'device' */ > - data[i] = fakedata[j]; > +// data[i] = fakedata[j]; > + put_unaligned_le16(fakedata[j], ((u8 *)(&data[i])) + 1); > len += 2; > } > } > > - iio_push_to_buffers_with_timestamp(indio_dev, data, > + iio_push_to_buffers_with_ts_unaligned(indio_dev, ((u8 *)(data)) + 1, indio_dev->scan_bytes - 8, > iio_get_time_ns(indio_dev)); > > > v1 description: > > I finally got around to do a manual audit of all the calls to > iio_push_to_buffers_with_timestamp() which has the somewhat odd requirements > of: > 1. 8 byte alignment of the provided buffer. > 2. space for an 8 byte naturally aligned timestamp to be inserted at the > end. > > Unfortunately there were rather a lot of these left, but time to bite the bullet > and clean them up. > > As discussed previous in > https://lore.kernel.org/linux-iio/20200920112742.170751-1-jic23@kernel.org/ > it is not easy to fix the alignment issue without requiring a bounce buffer. > This final part of the 4 sets of fixes is concerned with the cases where > bounce buffers are the proposed solutions. > > In these cases we have hardware that reads a prefix that we wish to > drop. That makes it hard to directly read the data into the correct location. > > Rather than implementing bouce buffers in each case, this set provides some > magic in the core to handle them via a new function. > iio_push_to_buffers_with_ts_na() - non aligned > > Note this is totally untested as I don't have suitable hardware or emulation. > I can fake something up in the dummy driver or via QEMU but I definitely want > both eyes and testing on this series! > > Jonathan Cameron (4): > iio: core: Introduce iio_push_to_buffers_with_ts_unaligned() > iio: adc: ti-adc108s102: Fix alignment of buffer pushed to iio > buffers. > iio: gyro: mpu3050: Fix alignment and size issues with buffers. > iio: imu: adis16400: Fix buffer alignment requirements. > > drivers/iio/adc/ti-adc108s102.c | 11 ++++---- > drivers/iio/gyro/mpu3050-core.c | 24 ++++++++-------- > drivers/iio/imu/adis16400.c | 20 ++++++++++---- > drivers/iio/industrialio-buffer.c | 46 +++++++++++++++++++++++++++++++ > include/linux/iio/buffer.h | 4 +++ > include/linux/iio/iio-opaque.h | 4 +++ > 6 files changed, 86 insertions(+), 23 deletions(-) >