Hi there! I’ve been working with spi interface of duo using spidev linux library, and found out that maximum tx buffer size to send data is 4096 bytes. I can not change file /sys/module/spidev/parameters/bufsize as it is write-protected, so i wonder, is there a legal way to increase spi buffer size? It seems to me, that i can change this value when building duo-buildroot-sdk, but i also couldn’t find any configs related to that in repository. Thanks in advance!
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To support running metastatic i use loadable kernel modules
Specify the bufsize as option
insmod /lib/modules/5.10.4-tag-/drivers/spi/spidev.ko bufsiz=20480
Have SPI LoRa SX1262 and 3.5" 320x480 SPI Display here
Milk-V DUO 256
And
Milk-V DUO 64 with USB keyboard mouse input 2.0" 320x240 SPI Display and SPI SX1262 LoRa
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yep, this is great idea, but i’d like to keep default buildroot-sdk image as i’m also working with camera sdk. Maybe someone knows how to change this bufsiz varaible from buildroot side? I can see sources of spidev driver in buildroot-sdk repo in duo-buildroot-sdk/linux_5.10/drivers/spi/spidev.c and there is bufsiz variable. Can i simply change it to my desired value and rebuild image w/o any unexpected consequences? Thank you!
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Ok, i did also try to pass the parameter from u-boot but my attempts it did stop the boot process for some reason
but you could edit the kernel source and change the default size ?
./linux_5.10/drivers/spi/
spidev.c
line 85
static unsigned bufsiz = 4096;
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Yep, i did it right now, image built successfully within docker, i’ll test the results and let you know about it.
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Well, as i expected, it couldn’t be so easy) Right now i have bufsiz 32768 bytes in /sys/module/spidev/parameters that i changed in spidev sources of buildroot drivers. Spidev still working fine, i can transfer data, but maximum tx buffer size is still 4096, and when im trying to transfer message more than 4096 bytes i got return code -1 from ioctl.
It seems to me, that i need to change something else to let kernel know that bufsiz is more than 4096…
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Oh, i set to max 32767
cat /sys/module/spidev/parameters/bufsiz ?
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