Merge tag 'driver-core-5.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core updates from Greg KH:
 "Here is the "big" set of driver core changes for 5.7-rc1.

  Nothing huge in here, just lots of little firmware core changes and
  use of new apis, a libfs fix, a debugfs api change, and some driver
  core deferred probe rework.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'driver-core-5.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (44 commits)
  Revert "driver core: Set fw_devlink to "permissive" behavior by default"
  driver core: Set fw_devlink to "permissive" behavior by default
  driver core: Replace open-coded list_last_entry()
  driver core: Read atomic counter once in driver_probe_done()
  libfs: fix infoleak in simple_attr_read()
  driver core: Add device links from fwnode only for the primary device
  platform/x86: touchscreen_dmi: Add info for the Chuwi Vi8 Plus tablet
  platform/x86: touchscreen_dmi: Add EFI embedded firmware info support
  Input: icn8505 - Switch to firmware_request_platform for retreiving the fw
  Input: silead - Switch to firmware_request_platform for retreiving the fw
  selftests: firmware: Add firmware_request_platform tests
  test_firmware: add support for firmware_request_platform
  firmware: Add new platform fallback mechanism and firmware_request_platform()
  Revert "drivers: base: power: wakeup.c: Use built-in RCU list checking"
  drivers: base: power: wakeup.c: Use built-in RCU list checking
  component: allow missing unbind callback
  debugfs: remove return value of debugfs_create_file_size()
  debugfs: Check module state before warning in {full/open}_proxy_open()
  firmware: fix a double abort case with fw_load_sysfs_fallback
  arch_topology: Fix putting invalid cpu clk
  ...

3 files changed, 110 insertions, 0 deletions

diff --git a/Documentation/driver-api/firmware/fallback-mechanisms.rst b/Documentation/driver-api/firmware/fallback-mechanisms.rst
index 8b041d0ab426..036383dad6d6 100644
--- a/Documentation/driver-api/firmware/fallback-mechanisms.rst
+++ b/Documentation/driver-api/firmware/fallback-mechanisms.rst
@@ -202,3 +202,106 @@ the following file:
 
 If you echo 0 into it means MAX_JIFFY_OFFSET will be used. The data type
 for the timeout is an int.
+
+EFI embedded firmware fallback mechanism
+========================================
+
+On some devices the system's EFI code / ROM may contain an embedded copy
+of firmware for some of the system's integrated peripheral devices and
+the peripheral's Linux device-driver needs to access this firmware.
+
+Device drivers which need such firmware can use the
+firmware_request_platform() function for this, note that this is a
+separate fallback mechanism from the other fallback mechanisms and
+this does not use the sysfs interface.
+
+A device driver which needs this can describe the firmware it needs
+using an efi_embedded_fw_desc struct:
+
+.. kernel-doc:: include/linux/efi_embedded_fw.h
+   :functions: efi_embedded_fw_desc
+
+The EFI embedded-fw code works by scanning all EFI_BOOT_SERVICES_CODE memory
+segments for an eight byte sequence matching prefix; if the prefix is found it
+then does a sha256 over length bytes and if that matches makes a copy of length
+bytes and adds that to its list with found firmwares.
+
+To avoid doing this somewhat expensive scan on all systems, dmi matching is
+used. Drivers are expected to export a dmi_system_id array, with each entries'
+driver_data pointing to an efi_embedded_fw_desc.
+
+To register this array with the efi-embedded-fw code, a driver needs to:
+
+1. Always be builtin to the kernel or store the dmi_system_id array in a
+   separate object file which always gets builtin.
+
+2. Add an extern declaration for the dmi_system_id array to
+   include/linux/efi_embedded_fw.h.
+
+3. Add the dmi_system_id array to the embedded_fw_table in
+   drivers/firmware/efi/embedded-firmware.c wrapped in a #ifdef testing that
+   the driver is being builtin.
+
+4. Add "select EFI_EMBEDDED_FIRMWARE if EFI_STUB" to its Kconfig entry.
+
+The firmware_request_platform() function will always first try to load firmware
+with the specified name directly from the disk, so the EFI embedded-fw can
+always be overridden by placing a file under /lib/firmware.
+
+Note that:
+
+1. The code scanning for EFI embedded-firmware runs near the end
+   of start_kernel(), just before calling rest_init(). For normal drivers and
+   subsystems using subsys_initcall() to register themselves this does not
+   matter. This means that code running earlier cannot use EFI
+   embedded-firmware.
+
+2. At the moment the EFI embedded-fw code assumes that firmwares always start at
+   an offset which is a multiple of 8 bytes, if this is not true for your case
+   send in a patch to fix this.
+
+3. At the moment the EFI embedded-fw code only works on x86 because other archs
+   free EFI_BOOT_SERVICES_CODE before the EFI embedded-fw code gets a chance to
+   scan it.
+
+4. The current brute-force scanning of EFI_BOOT_SERVICES_CODE is an ad-hoc
+   brute-force solution. There has been discussion to use the UEFI Platform
+   Initialization (PI) spec's Firmware Volume protocol. This has been rejected
+   because the FV Protocol relies on *internal* interfaces of the PI spec, and:
+   1. The PI spec does not define peripheral firmware at all
+   2. The internal interfaces of the PI spec do not guarantee any backward
+   compatibility. Any implementation details in FV may be subject to change,
+   and may vary system to system. Supporting the FV Protocol would be
+   difficult as it is purposely ambiguous.
+
+Example how to check for and extract embedded firmware
+------------------------------------------------------
+
+To check for, for example Silead touchscreen controller embedded firmware,
+do the following:
+
+1. Boot the system with efi=debug on the kernel commandline
+
+2. cp /sys/kernel/debug/efi/boot_services_code? to your home dir
+
+3. Open the boot_services_code? files in a hex-editor, search for the
+   magic prefix for Silead firmware: F0 00 00 00 02 00 00 00, this gives you
+   the beginning address of the firmware inside the boot_services_code? file.
+
+4. The firmware has a specific pattern, it starts with a 8 byte page-address,
+   typically F0 00 00 00 02 00 00 00 for the first page followed by 32-bit
+   word-address + 32-bit value pairs. With the word-address incrementing 4
+   bytes (1 word) for each pair until a page is complete. A complete page is
+   followed by a new page-address, followed by more word + value pairs. This
+   leads to a very distinct pattern. Scroll down until this pattern stops,
+   this gives you the end of the firmware inside the boot_services_code? file.
+
+5. "dd if=boot_services_code? of=firmware bs=1 skip=<begin-addr> count=<len>"
+   will extract the firmware for you. Inspect the firmware file in a
+   hexeditor to make sure you got the dd parameters correct.
+
+6. Copy it to /lib/firmware under the expected name to test it.
+
+7. If the extracted firmware works, you can use the found info to fill an
+   efi_embedded_fw_desc struct to describe it, run "sha256sum firmware"
+   to get the sha256sum to put in the sha256 field.
diff --git a/Documentation/driver-api/firmware/lookup-order.rst b/Documentation/driver-api/firmware/lookup-order.rst
index 88c81739683c..6064672a782e 100644
--- a/Documentation/driver-api/firmware/lookup-order.rst
+++ b/Documentation/driver-api/firmware/lookup-order.rst
@@ -12,6 +12,8 @@ a driver issues a firmware API call.
   return it immediately
 * The ''Direct filesystem lookup'' is performed next, if found we
   return it immediately
+* The ''Platform firmware fallback'' is performed next, but only when
+  firmware_request_platform() is used, if found we return it immediately
 * If no firmware has been found and the fallback mechanism was enabled
   the sysfs interface is created. After this either a kobject uevent
   is issued or the custom firmware loading is relied upon for firmware
diff --git a/Documentation/driver-api/firmware/request_firmware.rst b/Documentation/driver-api/firmware/request_firmware.rst
index f62bdcbfed5b..cd076462d235 100644
--- a/Documentation/driver-api/firmware/request_firmware.rst
+++ b/Documentation/driver-api/firmware/request_firmware.rst
@@ -25,6 +25,11 @@ firmware_request_nowarn
 .. kernel-doc:: drivers/base/firmware_loader/main.c
    :functions: firmware_request_nowarn
 
+firmware_request_platform
+-------------------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: firmware_request_platform
+
 request_firmware_direct
 -----------------------
 .. kernel-doc:: drivers/base/firmware_loader/main.c