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([2600:8803:e7e4:500:74a6:843b:f33:21ae]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-40a99787738sm4509503fac.15.2026.02.07.10.09.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Feb 2026 10:09:36 -0800 (PST) Message-ID: <8fbfcf7c-4acd-4a7f-a5a5-34baad84e1b2@baylibre.com> Date: Sat, 7 Feb 2026 12:09:34 -0600 Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] spi: allow ancillary devices to share parent's chip selects To: Antoniu Miclaus , Lars-Peter Clausen , Michael Hennerich , Jonathan Cameron , =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Olivier Moysan , Mark Brown , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org References: Content-Language: en-US From: David Lechner In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/6/26 10:07 AM, Antoniu Miclaus wrote: > When registering an ancillary SPI device, the current code flags a chip > select conflict with the parent device. This happens because the > ancillary device intentionally uses one of the parent's chip selects, > but __spi_add_device() checks against all existing devices including > the parent. > > Allow this by passing the parent device pointer to __spi_add_device() > and skipping the conflict check when the existing device is the parent. > ... > static int spi_dev_check(struct device *dev, void *data) > { > struct spi_device *spi = to_spi_device(dev); > - struct spi_device *new_spi = data; > + struct spi_dev_check_info *info = data; > + struct spi_device *new_spi = info->new_spi; > int status, idx; > > + /* > + * When registering an ancillary device, skip checking against the > + * parent device since the ancillary is intentionally using one of > + * the parent's chip selects. > + */ > + if (info->parent && spi == info->parent) spi should never be NULL (or we would get a segfault later), so if `(spi == info->parent)` should be enough. > + return 0; > + Reviewed-by: David Lechner