Howto known uncompressed length when uncompress_fd_to_buf

[Sascha Hauer]

On Tue, Dec 04, 2012 at 09:42:42AM +0800, 张忠山 wrote:
> In message <20121203095534.GL10369 at pengutronix.de> Sascha Hauer wrote:
> > On Fri, Nov 30, 2012 at 07:03:36PM +0800, 张忠山 wrote:
> > > the function uncompress_fd_to_buf has no parameter to return
> > > the uncompressed length, How to get the uncompressed content
> > > length?
> >
> > AFAIK the uncompressed size is not contained in the compressed data
> > You would have to uncompress to a file and use this afterwards.
> > If I understand correctly you want to load a FPGA firmware which you
> > have in compressed form. What I would do is:
> >
> > - uncompress the firmware in a script rather than uncompress it from
> >   C code.
> > - write a command to flash the firmware.
> >
> But if uncompress it to a device file, like /dev/tmpmem. the file size
> is the device size, not the uncompressed size.
> 
> So now I uncompressed it to a file in C code using uncompress_fd_to_fd,
> then use lseek to get the current position of target file. That is the
> uncompressed size.

Why don't you uncompress to a regular file (i.e. /tmp/foo) rather than
to the device file?

Sascha


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