Hello Pavel! On 28.09.17 18:24, Pavel Machek wrote: > Hi! > >>> Ok, makes sense. How does the board look? >> Did you mean a photo? Sure http://i.imgur.com/OShLIJx.jpg > Thanks. > >>>> The delay between data sends to SPI board should be at least 10 ms >>>> I think it will be bad idea to use shared workqueue from kernel, >>>> so I create separate single threaded work queue :) >>> If workqueue support in led core can not take 10 msec wait, we should >>> fix it, not add hacks around... >> Could you please explain or give a example? >> Because it's not clear for me, how I can use it. > You use cdev.brightness_set_blocking instead of brightness_set... I tried to use cdev.brightness_set_blocking, but instead working LEDs I got kernel NULL pointer dereference error. [ 760.397833] [<8053d858>] (led_set_brightness) from [<8053db78>] (led_classdev_unregister+0x58/0xa0) [ 760.406892] [<8053db20>] (led_classdev_unregister) from [<8053dbd4>] (devm_led_classdev_release+0x14/0x18) [ 760.416550] r5:bcc87e88 r4:bc7ff200 [ 760.420177] [<8053dbc0>] (devm_led_classdev_release) from [<803f0210>] (release_nodes+0x19c/0x1c4) [ 760.429149] [<803f0074>] (release_nodes) from [<803f0304>] (devres_release_all+0x4c/0x54) [ 760.437330] r10:00000000 r9:bcc86000 r8:80107304 r7:00000081 r6:bc2c9a34 r5:7f00059c [ 760.445249] r4:bc2c9a00 [ 760.447812] [<803f02b8>] (devres_release_all) from [<803ecb7c>] (__device_release_driver+0x8c/0xe8) [ 760.456861] r4:bc2c9a00 r3:00000000 [ 760.460481] [<803ecaf0>] (__device_release_driver) from [<803ed2b8>] (driver_detach+0x8c/0xb4) [ 760.469096] r5:7f00059c r4:bc2c9a00 [ 760.472715] [<803ed22c>] (driver_detach) from [<803ec8d4>] (bus_remove_driver+0x6c/0x94) [ 760.480810] r6:7e98ebc0 r5:0128cd64 r4:7f00059c r3:bca90000 [ 760.486547] [<803ec868>] (bus_remove_driver) from [<803ed924>] (driver_unregister+0x44/0x50) [ 760.494989] r4:7f00059c r3:bc782d80 [ 760.498614] [<803ed8e0>] (driver_unregister) from [<7f00032c>] (cr0014114_driver_exit+0x14/0x1c [leds_cr0014114]) [ 760.508879] r4:7f0005d8 r3:7f000318 [ 760.512512] [<7f000318>] (cr0014114_driver_exit [leds_cr0014114]) from [<8018418c>] (SyS_delete_module+0x100/0x1bc) [ 760.522966] [<8018408c>] (SyS_delete_module) from [<80107160>] (ret_fast_syscall+0x0/0x3c) [ 760.531235] r5:00000002 r4:7e98edac > > Pavel -- Best regards, Oleh Kravchenko
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