[haiku-bugs] [Haiku] #8530: EHCI usb driver does not support unaligned read/writes
- From: "pulkomandy" <trac@xxxxxxxxxxxx>
- Date: Sun, 06 May 2012 11:52:29 -0000
#8530: EHCI usb driver does not support unaligned read/writes
-------------------------+------------------------------
Reporter: pulkomandy | Owner: mmlr
Type: bug | Status: new
Priority: normal | Milestone: R1
Component: Drivers/USB | Version: R1/Development
Keywords: | Blocked By:
Blocking: | Has a Patch: 0
Platform: All |
-------------------------+------------------------------
I'm trying to perform some simple sector read/write operations on an usb
mass storage device (SD card reader).
The following code works fine :
{{{
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
int main(void)
{
char* buffer = malloc(512);
int fd = open("/dev/disk/usb/0/3/raw", O_RDONLY);
lseek(fd, 8192, SEEK_SET);
if (fd < 0)
perror("open error");
if (read(fd, buffer, 1) == -1)
perror("read error");
close(fd);
free(buffer);
}
}}}
But this one doesn't :
{{{
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
int main(void)
{
char buffer[512];
int fd = open("/dev/disk/usb/0/3/raw", O_RDONLY);
lseek(fd, 8192, SEEK_SET);
if (fd < 0)
perror("open error");
if (read(fd, buffer, 1) == -1)
perror("read error");
close(fd);
}
}}}
The only difference is the way buffer is allocated. Our malloc happens to
align memory to pages, while allocating on the stack obviously doesn't.
Following message is seen in error log :
{{{
KERN: usb error transfer 0: data buffer spans across multiple areas!
KERN: usb error ehci -1: failed to add pending transfer
}}}
From then on, the device is not accessible anymore by any means and needs
to be unplugged/replugged.
--
Ticket URL: <http://dev.haiku-os.org/ticket/8530>
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