Re: [PATCH v3 1/5] seq_file: provide an analogue of print_hex_dump()

Andy Shevchenko
2014-09-01T09:10:25Z

On Mon, 2014-09-01 at 10:58 +0200, Geert Uytterhoeven wrote:
> Hi Andy,
>
> On Mon, Sep 1, 2014 at 10:36 AM, Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> >> ... and extra copying for no good reason. Why not check that we have
> >> enough space in buffer and generate directly into it? See what e.g.
> >> seq_escape() is doing...
> >
> > What about this variant?
>
> I think it needs a call to seq_set_overflow() in case the buffer is too small,
> so the caller will retry with a bigger buffer.

Yes, in two places it would be useful to do.

But what the condition for "buffer is too small", the same groupsize * 2
+ 1 or you mean something else?

>
> >
> > @@ -794,6 +795,47 @@ void seq_pad(struct seq_file *m, char c)
> > }
> > EXPORT_SYMBOL(seq_pad);
> >
> > +/* Analogue of print_hex_dump() */
> > +void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
> > + int rowsize, int groupsize, const void *buf, size_t len,
> > + bool ascii)
> > +{
> > + const u8 *ptr = buf;
> > + int i, linelen, remaining = len;
> > + int ret;
> > +
> > + if (rowsize != 16 && rowsize != 32)
> > + rowsize = 16;
> > +
> > + for (i = 0; i < len; i += rowsize) {
> > + linelen = min(remaining, rowsize);
> > + remaining -= rowsize;
> > +
> > + ret = seq_printf(m, "%s", prefix_str);
> > + if (ret < 0)
> > + break;
> > +
> > + if (prefix_type == DUMP_PREFIX_ADDRESS)
> > + ret = seq_printf(m, "%p: ", ptr + i);
> > + else if (prefix_type == DUMP_PREFIX_OFFSET)
> > + ret = seq_printf(m, "%.8x: ", i);
> > + if (ret < 0)
> > + break;
> > +
> > + if (m->size < m->count + groupsize * 2 + 1)
> > + break;
> > +
> > + hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
> > + m->buf + m->count, m->size - m->count,
> > + ascii);
> > +
> > + ret = seq_putc(m, '\n');
> > + if (ret < 0)
> > + break;
> > + }
> > +}
> > +EXPORT_SYMBOL(seq_hex_dump);
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds

--
Andy Shevchenko <andriy.shevchenko@intel.com>
Intel Finland Oy