efi_file_install() and efi_download_install() are both used to install
onto existing handles.  There is therefore no need to allow for each
of their calls to InstallMultipleProtocolInterfaces() to create a new
handle.

By passing the handle directly (rather than a pointer to the handle),
we avoid potential confusion (and erroneous debug message colours).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

We currently treat network devices as available for use via the SNP
API only if RX queue processing has been frozen.  (This is similar in
spirit to the way that RX queue processing is frozen for the network
device currently exposed via the PXE API.)

The default state of a freshly created network device is for the RX
queue to not be frozen, and thus to be unavailable for use via SNP.
This causes problems when devices are added through code paths other
than _efidrv_start() (which explicitly releases devices for use via
SNP).

We don't actually need to freeze RX queue processing, since calls via
the SNP API will always use netdev_poll() rather than net_poll(), and
so will never trigger the RX queue processing code path anyway.

We can therefore simplify the code to use a single global flag to
indicate whether network devices are claimed for use by iPXE or
available for use via SNP.  Using a global flag allows the default
state for dynamically created network devices to behave sensibly.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Exploit the redefinition of iPXE error codes to include a "platform
error code" to allow for meaningful conversion of EFI_STATUS values to
iPXE errors and vice versa.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Expose iPXE's images as a UEFI file system, allowing the booted image
to access all images downloaded by iPXE.

This functionality is complementary to the custom iPXE download
protocol.  The iPXE download protocol allows a booted image to utilise
iPXE to download arbitrary URIs, but requires the booted image to
specifically support the custom iPXE download protocol.  The new
functionality limits the booted image to accessing only files that
were already downloaded by iPXE (e.g. as part of a script), but can
work with any generic UEFI image (e.g. the UEFI shell).  Both
protocols are provided simultaneously, and are attached to the SNP
device handle.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

iPXE exposes some extended capabilities via the PXE FILE API to allow
NBPs such as pxelinux to use protocols other than TFTP.  Provide an
equivalent interface as a UEFI protocol so that EFI binaries may also
take advantage of iPXE's extended capabilities.

This can be used with a patched version of elilo, for example:

  http://comments.gmane.org/gmane.comp.boot-loaders.elilo.general/147

Signed-off-by: Michael Brown <mcb30@ipxe.org>