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([2600:8803:e7e4:500:bd39:740e:f70f:5f7d]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-6611a78b02fsm1355053eaf.9.2026.01.16.15.12.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Jan 2026 15:12:11 -0800 (PST) Message-ID: <8e12d2a5-3780-45af-a70c-4c112184fcc6@baylibre.com> Date: Fri, 16 Jan 2026 17:12:09 -0600 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 3/9] spi: support controllers with multiple data lanes To: Andy Shevchenko , Mark Brown Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Marcelo Schmitt , Michael Hennerich , =?UTF-8?Q?Nuno_S=C3=A1?= , Jonathan Cameron , Andy Shevchenko , Sean Anderson , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org References: <20260112-spi-add-multi-bus-support-v5-0-295f4f09f6ba@baylibre.com> <20260112-spi-add-multi-bus-support-v5-3-295f4f09f6ba@baylibre.com> <22a6a28c-0f03-4571-b2a0-8c9b82788b68@sirena.org.uk> Content-Language: en-US From: David Lechner In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/12/26 1:35 PM, Andy Shevchenko wrote: > On Mon, Jan 12, 2026 at 07:11:26PM +0000, Mark Brown wrote: >> On Mon, Jan 12, 2026 at 09:07:17PM +0200, Andy Shevchenko wrote: >>> On Mon, Jan 12, 2026 at 11:45:21AM -0600, David Lechner wrote: > > ... > >>>> + /* Multi-lane SPI controller support. */ >>>> + u32 tx_lane_map[SPI_DEVICE_DATA_LANE_CNT_MAX]; >>>> + u32 num_tx_lanes; >>>> + u32 rx_lane_map[SPI_DEVICE_DATA_LANE_CNT_MAX]; >>>> + u32 num_rx_lanes; >> >>> This adds 72 bytes in _each_ instance of spi_device on the platforms that do >>> not use the feature and might not ever use it. Can we move to the pointer >>> and allocate the mentioned fields separately, please? >> >> Do we have real systems where we have enough SPI devices for anyone to >> care? > > Define "enough" :-) To me even dozen of devices is enough (it gets almost a 1kB > of space) esp. if we are talking about quite low profile embedded systems. > We could make it u8 and save the same amount (on 64-bit systems) while avoiding the extra complexity of separate allocation. I'm not particularly keen on requiring `/bits/ 8` in the devicetree though since it is unusual and often trips people up.