[Qemu-devel] Re: [PATCH][SEABIOS] Move qemu config port access functions into separate file.

[Gleb Natapov]

On Thu, Sep 17, 2009 at 09:24:11PM -0400, Kevin O'Connor wrote:
> On Thu, Sep 17, 2009 at 12:57:28PM +0300, Gleb Natapov wrote:
> > The configuration interface should be able to read streams of data
> > though.  Qemu uses it to pass additional ACPI tables for instance. So
> > it not just simple key->value interface. get_config_u32("ShowBootMenu")
> > will work for simple cases but how can we express stream semantic? May be:
> > 
> > table_count = get_config_u16("AdditionalAcpiCount")
> > select_config("AdditionalAcpiTables");
> > for (i=0; i<table_count; i++) {
> >    len = config_read(table[i], table_len[i]);
> > }
> 
> On coreboot there is the Coreboot FileSystem (CBFS).  Basically, the
> flash stores a series of named files, and SeaBIOS knows how to iterate
> through them.  So, for instance, one might find the file
> "pci1013,00b8.rom" which contains an option rom for pci device
> 1013:00b8, or one might find "floppyimg/FreeDOS" with an image of a
> floppy to be emulated.
> 
> So, ideally qemu would do something similar.  Maybe something like:
Qemu already does something different. For instance acpi tables are
transfered as stream formated like this:
<table count><1 table length><table data><2 table length><table data>
...<n table length><table data>

I don't think qemu should expose file system API to a BIOS.

> copy_config_file("AdditionalAcpiTables", destfileptr, destfilemaxlen).
> The exact mechanism for extracting the info is flexible.  To be
> compatible with the CBFS interface, seabios just needs a way to "walk"
> the list of files, find out how big a given file is, and be able to
> copy the file to ram.
> 
> If anyone is curious, the cbfs functions are in src/coreboot.c - the
> main interface is:
> 
> // Find the file with the given filename.
> struct cbfs_file *cbfs_findfile(const char *fname)
> // Find next file with the given filename prefix.
> struct cbfs_file *cbfs_findprefix(const char *prefix, struct cbfs_file *last)
> // Determine the uncompressed size of a datafile.
> u32 cbfs_datasize(struct cbfs_file *file)
> // Copy a file to memory (uncompressing if necessary)
> int cbfs_copyfile(struct cbfs_file *file, void *dst, u32 maxlen)
> 
> -Kevin

--
                        Gleb.