On 12/03/10 13:59, bkankur wrote: > > Dear Friends, > > I am using polling based serial driver by specifying buffer size(cbuf->len) > to zero through configuration tool. > When I call scanf function from application layer, I found that it is > calling serial_read function from file > packages\io\serial\current\src\common\serial.c. > > For given function, static Cyg_ErrNo serial_read(cyg_io_handle_t handle, > void *_buf, cyg_uint32 *len) > I printed the argument values and found that *len=-1, which makes "while > (size++ < *len) " condition true always and my program gets stuck there.
That certainly doesn't seem right. *len should not be -1 while in the loop in serial_read (presumably that's the loop you mean). That would imply it's been called with *len==-1. But the libc stream support should be using a positive integer of at least 1. (refill_read_buffer() in stream.cxx is the key here.) Just in case, you may want to increase your stack sizes in case something's getting scribbled on due to stack overflow. > I did similar thing for serial_write and I got *len value correct when I > call Printf function from user application. > > I try to debug the /libc/sdio/current/src/input/scanf.cxx, but I couldn't > understand it. Can anyone please guide me where to look at for the error, in > my case *len = -1 which should be greater than 1 ? Double check what the value of *len is at the entry to serial_read. You can also try stepping through Cyg_StdioStream::refill_read_buffer() to see what it's calling it with. Jifl -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
