On Sat, Feb 25, 2012 at 10:24:09AM +0100, Frank Danapfel wrote:
> Hello,
>
> for a project I'm working on I need to communicate with a device
> (Arduino Uno) at a custom baudrate via a USB serial connection. The
> device is accessed via the "cdc-acm" kernel module, which doesn't seem
> to allow the setting of serial port parameters:
>
> # lsmod|grep -i acm
> cdc_acm 27935 0
> # dmesg
> ...
> [71475.837970] usbcore: registered new interface driver cdc_acm
> [71475.837972] cdc_acm: USB Abstract Control Model driver for USB modems and
> ISDN adapters
> (after plugging in the hardware (an Arduino Uno)
> [71731.773090] usb 6-2: new full-speed USB device number 5 using uhci_hcd
> [71731.958129] usb 6-2: New USB device found, idVendor=2341, idProduct=0001
> [71731.958139] usb 6-2: New USB device strings: Mfr=1, Product=2,
> SerialNumber=220
> [71731.958146] usb 6-2: Product: Arduino Uno
> [71731.958151] usb 6-2: Manufacturer: Arduino (www.arduino.cc)
> [71731.958157] usb 6-2: SerialNumber: 64932343638351A08180
> [71731.963281] cdc_acm 6-2:1.0: ttyACM0: USB ACM device
>
> # setserial /dev/ttyACM0 spd_hi
> Cannot set serial info: Invalid argument
>
> # strace setserial /dev/ttyACM0 spd_hi
> execve("/bin/setserial", ["setserial", "/dev/ttyACM0", "spd_hi"], [/* 66 vars
> */]) = 0
> brk(0) = 0x1ed1000
> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
> 0x7fd9d311c000
> access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
> open("/etc/ld.so.cache", O_RDONLY) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=156038, ...}) = 0
> mmap(NULL, 156038, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fd9d30f5000
> close(3) = 0
> open("/lib64/libc.so.6", O_RDONLY) = 3
> read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0p\24B\2262\0\0\0"...,
> 832) = 832
> fstat(3, {st_mode=S_IFREG|0755, st_size=1947608, ...}) = 0
> mmap(0x3296400000, 3769592, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
> 0) = 0x3296400000
> mprotect(0x329658e000, 2097152, PROT_NONE) = 0
> mmap(0x329678e000, 20480, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x18e000) = 0x329678e000
> mmap(0x3296793000, 21752, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x3296793000
> close(3) = 0
> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
> 0x7fd9d30f4000
> mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
> 0x7fd9d30f2000
> arch_prctl(ARCH_SET_FS, 0x7fd9d30f2720) = 0
> mprotect(0x329678e000, 16384, PROT_READ) = 0
> mprotect(0x329621e000, 4096, PROT_READ) = 0
> munmap(0x7fd9d30f5000, 156038) = 0
> open("/dev/ttyACM0", O_RDWR|O_NONBLOCK) = 3
> ioctl(3, TIOCGSERIAL, 0x7fff692984e0) = 0
> ioctl(3, TIOCSSERIAL, 0x7fff69298530) = -1 EINVAL (Invalid argument)
> dup(2) = 4
> fcntl(4, F_GETFL) = 0x8002 (flags O_RDWR|O_LARGEFILE)
> brk(0) = 0x1ed1000
> brk(0x1ef2000) = 0x1ef2000
> brk(0) = 0x1ef2000
> fstat(4, {st_mode=S_IFCHR|0600, st_rdev=makedev(136, 1), ...}) = 0
> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
> 0x7fd9d311b000
> lseek(4, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
> write(4, "Cannot set serial info: Invalid "..., 41Cannot set serial info:
> Invalid argument
> ) = 41
> close(4) = 0
> munmap(0x7fd9d311b000, 4096) = 0
> exit_group(1) = ?
>
> I've tested this on Fedora 15 with kernel 2.6.42.3-2.fc15.x86_64.
>
> There was an old thread on this list about implementing TIOCGSERIAL in
> the cdc-acm module
> (http://permalink.gmane.org/gmane.linux.usb.general/9236).
>
> Would it be possible to add support for TIOCSSERIAL in cdc-acm as well?
I just added that patch to the tree a few hours ago, it will show up in
the 3.4 kernel release.
greg k-h
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