efi/libstub: Describe RNG functions

Provide descriptions for the functions invoking the EFI_RNG_PROTOCOL.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://lore.kernel.org/r/20200221114716.4372-1-xypron.glpk@gmx.de
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c
index 21e7e9325219fe73c38cbc2eb81a311b85c441a4..24aa375353724abd5339f4d71179c92330bf3170 100644 (file)
--- a/drivers/firmware/efi/libstub/random.c
+++ b/drivers/firmware/efi/libstub/random.c
@@ -25,6 +25,17 @@ union efi_rng_protocol {
        } mixed_mode;
 };
 
+/**
+ * efi_get_random_bytes() - fill a buffer with random bytes
+ * @size:      size of the buffer
+ * @out:       caller allocated buffer to receive the random bytes
+ *
+ * The call will fail if either the firmware does not implement the
+ * EFI_RNG_PROTOCOL or there are not enough random bytes available to fill
+ * the buffer.
+ *
+ * Return:     status code
+ */
 efi_status_t efi_get_random_bytes(unsigned long size, u8 *out)
 {
        efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
@@ -38,6 +49,19 @@ efi_status_t efi_get_random_bytes(unsigned long size, u8 *out)
        return efi_call_proto(rng, get_rng, NULL, size, out);
 }
 
+/**
+ * efi_random_get_seed() - provide random seed as configuration table
+ *
+ * The EFI_RNG_PROTOCOL is used to read random bytes. These random bytes are
+ * saved as a configuration table which can be used as entropy by the kernel
+ * for the initialization of its pseudo random number generator.
+ *
+ * If the EFI_RNG_PROTOCOL is not available or there are not enough random bytes
+ * available, the configuration table will not be installed and an error code
+ * will be returned.
+ *
+ * Return:     status code
+ */
 efi_status_t efi_random_get_seed(void)
 {
        efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;