Hi Alex, Jean, > > > It would take a broken shell to do what you describe, if that's > > > possible at all. The following command should answer your question: > > > > > > echo 0 > /sys/class/hwmon/hwmon0/device/pwm1_enable ; echo 255 > /tmp/pwm1 ; cat /tmp/pwm1 > > > > > > Here, it prints the expected error message, then 255. > > > > -------------------------------------------------------------------------- > > root at alex:~# echo 0 > /sys/class/hwmon/hwmon0/device/pwm1_enable ; echo > > 255 > /tmp/pwm1 ; cat /tmp/pwm1 > > bash: echo: write error: Invalid argument > > 0 > > 255 > > root at alex:~# cat /tmp/pwm1 > > 0 > > 255 > > -------------------------------------------------------------------------- > > > > As you can see it prints the error message, the 0 and the 255. And you > > can see both go into /temp/pwm1. > > > > Bummer. That's your shell keeping the initial output (which it failed > to write to pwm1_enable) in some internal buffer and writing it to pwm1 > later. I'd say shell bug, and a big one at that. And security-related, > too. I tested on my openSuse 10.3 laptop which has bash version > 3.2.25(1) as your system does, and couldn't reproduce the problem > there. Thus I would suspect a Ubuntu-specific patch. I just thought I'd throw in another test point. I was curious if the w83627ehf driver was somehow storing "0\n255" or some similar wrong behavior: # echo 1 > pwm3_enable # echo 175 > pwm3 # echo "0 > 175" > pwm3 # cat pwm3 175 # echo -e "0\n175" 0 175 # echo -e "0\n175" > pwm3 # cat pwm3 175 # dmesg | tail [ 291.436322] allocating slot 0, addr 2e for device 8860 [ 291.436323] found devid:8860 port:2e users:1 [ 291.436331] w83627ehf: Found W83627EHG chip at 0x290 [ 291.436536] releasing last user of superio-port 2e [ 301.088199] w83627ehf w83627ehf.656: Increasing fan3 clock divider from 2 to 4 [ 301.088233] w83627ehf w83627ehf.656: Increasing fan5 clock divider from 1 to 2 [ 302.644499] w83627ehf w83627ehf.656: Increasing fan5 clock divider from 2 to 4 [ 304.884458] w83627ehf w83627ehf.656: Increasing fan5 clock divider from 4 to 8 [ 309.069573] w83627ehf w83627ehf.656: Increasing fan5 clock divider from 8 to 16 [ 313.797610] w83627ehf w83627ehf.656: Increasing fan5 clock divider from 16 to 32 Alex, I wonder if your bash is creating a file with "0\n255" in it? Because I would feel fairly confident in saying the driver will not be able to store a string for later retrieval in pwm3, or pwm1. Hope that helps, David
