Re: [PATCH v3 1/2] spi: add new_device/delete_device sysfs interface

[Mark Brown <broonie@kernel.org>]

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On Mon, May 04, 2026 at 07:40:36AM +0000, Vishwaroop A wrote:
> Development boards such as the Jetson AGX Orin expose SPI buses
> on expansion headers (e.g. the 40-pin header) so that users can
> connect and interact with SPI peripherals from userspace. The
> standard way to get /dev/spidevB.C character device nodes for
> this purpose is to register spi_device instances backed by the
> spidev driver.

> +static ssize_t
> +new_device_store(struct device *dev, struct device_attribute *attr,
> +		 const char *buf, size_t count)
> +{

> +	mutex_lock(&ctlr->add_lock);
> +	status = __spi_add_device(spi, NULL);

This takes add_lock in a sysfs operation but spi_unregister_controller()
also does that while it's calling device_del on the controller's device
which will result in the sysfs files for the controller being deleted.
That'll deadlock...

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