On 1/7/21 8:06 PM, Jakub Kicinski wrote: > On Thu, 7 Jan 2021 11:00:35 -0800 Jakub Kicinski wrote: >> On Thu, 7 Jan 2021 10:48:56 +0100 Marc Kleine-Budde wrote: >>> +struct __packed tcan4x5x_map_buf { >>> + struct tcan4x5x_buf_cmd cmd; >>> + u8 data[256 * sizeof(u32)]; >>> +} ____cacheline_aligned; >> >> Interesting attribute combo, I must say. > > Looking at the rest of the patch I don't really see a reason for > __packed. Perhaps it can be dropped? It's the stream of bytes send via SPI to the chip. Here are both structs for reference: > +struct __packed tcan4x5x_buf_cmd { > + u8 cmd; > + __be16 addr; > + u8 len; > +}; This has to be packed, as I assume the compiler would add some space after the "u8 cmd" to align the __be16 naturally. > +struct __packed tcan4x5x_map_buf { > + struct tcan4x5x_buf_cmd cmd; > + u8 data[256 * sizeof(u32)]; > +} ____cacheline_aligned; Due to the packing of the struct tcan4x5x_buf_cmd it should have a length of 4 bytes. Without __packed, will the "u8 data" come directly after the cmd? Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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