Change in coreboot[master]: libpayload: Add libpayload_boot_device_read function

[Jakub Czapiga (Code Review)]

Jakub Czapiga has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/59492 )

Change subject: libpayload: Add libpayload_boot_device_read function
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libpayload: Add libpayload_boot_device_read function

This patch adds a new way of implementing flash access for libpayload.
Until now all reads had to be performed using cbfs_media, which is
obsolete. From now on all reads should be performed using
libpayload_boot_device_read(). This patch also provides a fallback
implementation of this function using cbfs_media, but it will be removed
in the future together with cbfs_media API.

Change-Id: I1babd2a8414ed9de3ca49903fcb4f036997b5ff3
Signed-off-by: Jakub Czapiga 
---
A payloads/libpayload/include/boot_device.h
M payloads/libpayload/include/libpayload.h
M payloads/libpayload/libc/Makefile.inc
A payloads/libpayload/libc/boot_device.c
4 files changed, 46 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/92/59492/1

diff --git a/payloads/libpayload/include/boot_device.h b/payloads/libpayload/include/boot_device.h
new file mode 100644
index 0000000..c2cf105
--- /dev/null
+++ b/payloads/libpayload/include/boot_device.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: BSD-3-Clause OR GPS-2.0-or-later */
+
+#ifndef _BOOT_DEVICE_H
+#define _BOOT_DEVICE_H
+
+#include <stddef.h>
+
+/**
+ * This is a boot device access function, which is used by libpayload to read data from
+ * the flash memory (or other boot device). It has to be implemented by payloads using
+ * FlashMap and libCBFS.
+ *
+ * @param buf The output buffer to which the data should be written to.
+ * @param offset Absolute offset in bytes of the requested boot device memory area. Not aligned.
+ * @param size Size in bytes of the requested boot device memory area. Not aligned.
+ *
+ * @returns Number of bytes returned to the buffer, or negative value on error. Typically should
+ *          be equal to the `size`, and not aligned forcefully.
+ */
+ssize_t libpayload_boot_device_read(void *buf, size_t offset, size_t size);
+
+#endif /* _BOOT_DEVICE_H */
diff --git a/payloads/libpayload/include/libpayload.h b/payloads/libpayload/include/libpayload.h
index e08d211..42748e3 100644
--- a/payloads/libpayload/include/libpayload.h
+++ b/payloads/libpayload/include/libpayload.h
@@ -64,6 +64,7 @@
 #include <sysinfo.h>
 #include <pci.h>
 #include <archive.h>
+#include <boot_device.h>

/* Double-evaluation unsafe min/max, for bitfields and outside of functions */
 #define __CMP_UNSAFE(a, b, op) ((a) op (b) ? (a) : (b))
diff --git a/payloads/libpayload/libc/Makefile.inc b/payloads/libpayload/libc/Makefile.inc
index f9006ae..74b710e 100644
--- a/payloads/libpayload/libc/Makefile.inc
+++ b/payloads/libpayload/libc/Makefile.inc
@@ -39,3 +39,4 @@
 libc-$(CONFIG_LP_LIBC) += coreboot.c
 libc-$(CONFIG_LP_LIBC) += fmap.c
 libc-$(CONFIG_LP_LIBC) += fpmath.c
+libc-$(CONFIG_LP_LIBC) += boot_device.c
diff --git a/payloads/libpayload/libc/boot_device.c b/payloads/libpayload/libc/boot_device.c
new file mode 100644
index 0000000..17bad0d
--- /dev/null
+++ b/payloads/libpayload/libc/boot_device.c
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: BSD-3-clause OR GPL-2.0-or-later */
+
+#include <boot_device.h>
+#include <cbfs.h>
+#include <stddef.h>
+
+/* Default fallback implementation using cbfs_media */
+__attribute__((weak)) ssize_t libpayload_boot_device_read(void *buf, size_t offset, size_t size)
+{
+	struct cbfs_media default_media;
+	struct cbfs_media *media = &default_media;
+	ssize_t ret = 0;
+
+	if (init_default_cbfs_media(media) != 0)
+		return 0;
+
+	media->open(media);
+	ret = media->read(media, buf, offset, size);
+	media->close(media);
+
+	return ret;
+}