How to change spi_ioc_transfer max length

Technical Support
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1

I tryed to connect the colibri to a microcontroller via spi. Messages over 4096 bit length are not successfully transfered. Below this limit all works fine. How can I change the set “max value” to 8192 or more? I am programming with c.

struct spi_ioc_transfer tr =
{

	.tx_buf = (unsigned long)tx,
	.rx_buf = (unsigned long)rx,
	.len = ARRAY_SIZE(tx), // limited to 4096 bytes!
	.delay_usecs = delay,
	.speed_hz = speed,
	.bits_per_word = bits,
};

...

retVal = ioctl(fd_SPI, SPI_IOC_MESSAGE(1), &tr);
2

4096 is the default buffer size used in spidev kernel module. You can change this using the spidev.bufsiz kernel module parameter.

See Maximum transfer size 4096 bytes with spidev driver for SPI on Colibri imx6 - Technical Support - Toradex Community