Re: [RFC 04/25] spi: gpio: Implement LSB First bitbang support
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2019-12-12 08:40:44
Also in:
linux-leds, linux-spi, lkml
Hi Andreas, On Thu, Dec 12, 2019 at 4:41 AM Andreas Färber [off-list ref] wrote:
Add support for slave DT property spi-lsb-first, i.e., SPI_LSB_FIRST mode.
Duplicate the inline helpers bitbang_txrx_be_cpha{0,1} as LE versions.
Make checkpatch.pl happy by changing "unsigned" to "unsigned int".
Conditionally call them from all the spi-gpio txrx_word callbacks.
Signed-off-by: Andreas Färber <afaerber@suse.de>Thanks for your patch!
quoted hunk ↗ jump to hunk
--- a/drivers/spi/spi-gpio.c +++ b/drivers/spi/spi-gpio.c@@ -135,25 +135,37 @@ static inline int getmiso(const struct spi_device *spi) static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, unsigned flags) { - return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); + if (unlikely(spi->mode & SPI_LSB_FIRST)) + return bitbang_txrx_le_cpha0(spi, nsecs, 0, flags, word, bits); + else + return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); }
Duplicating all functions sounds a bit wasteful to me.
What about reverting the word first, and calling the normal functions?
if (unlikely(spi->mode & SPI_LSB_FIRST)) {
if (bits <= 8)
word = bitrev8(word) >> (bits - 8);
else if (bits <= 16)
word = bitrev16(word) >> (bits - 16);
else
word = bitrev32(word) >> (bits - 32);
}
return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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