From: Mark Brown <broonie@kernel.org>
To: Jonas Rebmann <jre@pengutronix.de>
Cc: linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org,
Marc Kleine-Budde <mkl@pengutronix.de>,
kernel@pengutronix.de
Subject: Re: [PATCH 6/7] spi: spidev_test: add option to split message into multiple transfers
Date: Mon, 14 Sep 2026 19:04:04 +0100 [thread overview]
Message-ID: <aqg3FFSZDLe_WI9Q@sirena.org.uk> (raw)
In-Reply-To: <20260914-spi-sun4i-spidev_test-v1-6-72d6a3b38cee@pengutronix.de>
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On Mon, Sep 14, 2026 at 04:50:45PM +0200, Jonas Rebmann wrote:
> SPI_IOC_MESSAGE() submits a single SPI message containing one or more
> transfers. Introduce an option to allow splitting the message into
> multiple transfers.
> + size_t bytes_per_word = DIV_ROUND_UP(bits, 8);
> + int effective_transfers = min_t(int, transfers, DIV_ROUND_UP(len, bytes_per_word));
We divide by this and nothing stops us triggering a divide by 0.
> + struct spi_ioc_transfer tr[effective_transfers];
This could easily get very big if someone decides to test lots of small
transfers, it's probably worth moving off the stack at this point.
> + size_t len_per_transfer = ALIGN(DIV_ROUND_UP(len, effective_transfers), bytes_per_word);
The kernel's ALIGN() macro only works for powers of two.
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next prev parent reply other threads:[~2026-09-14 18:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-14 14:50 [PATCH 0/7] spi: spidev_test: new features Jonas Rebmann
2026-09-14 14:50 ` [PATCH 1/7] spi: spidev_test: include tools/include Jonas Rebmann
2026-09-14 14:50 ` [PATCH 2/7] spi: spidev_test: add compare mode Jonas Rebmann
2026-09-14 17:03 ` Mark Brown
2026-09-14 14:50 ` [PATCH 3/7] spi: spidev_test: allow disabling rx or tx buffers Jonas Rebmann
2026-09-14 17:20 ` Mark Brown
2026-09-14 14:50 ` [PATCH 4/7] spi: spidev_test: don't send 0x0 or 0xff Jonas Rebmann
2026-09-14 17:22 ` Mark Brown
2026-09-14 14:50 ` [PATCH 5/7] spi: spidev_test: send predictable data Jonas Rebmann
2026-09-14 14:50 ` [PATCH 6/7] spi: spidev_test: add option to split message into multiple transfers Jonas Rebmann
2026-09-14 18:04 ` Mark Brown [this message]
2026-09-14 14:50 ` [PATCH 7/7] spi: spidev_test: print TX on error Jonas Rebmann
2026-09-14 18:07 ` Mark Brown
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