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Andrey Smirnov
9fb4ab4d3d
Next record calucaltion can be reduced to a much more tivial ALIGN operation as follows: 1. Splitting 5 into 2 + 3 we get next = ((be16_to_cpu(rec->len) + 2 + 3) & ~3) - 2 (1) 2. Using ALIGN macro we reduce (1) to: ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2 (2) 3. Subsituting 'next' in original next record calucation we get: (void *)&rec->data[ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2] (3) 4. Converting array index to pointer arithmetic we convert (3) into: (void *)rec + sizeof(*rec) + ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2 (4) 5. Subsituting sizeof(*rec) with its value, 6, and substracting 2, in (4) we get: (void *)rec + ALIGN(be16_to_cpu(rec->len) + 2, 4) + 4 (5) 6. Since ALIGN(X, 4) + 4 == ALIGN(X + 4, 4), (5) can be converted to: (void *)rec + ALIGN(be16_to_cpu(rec->len) + 6, 4) (6) 5. Subsituting 6 in (6) to sizeof(*rec) we get: (void *)rec + ALIGN(be16_to_cpu(rec->len) + sizeof(*rec), 4) (7) Using expression (7) should make it more clear that next record is located by adding full size of the current record (payload + auxiliary data) aligned to 4 bytes, to the location of the current one. No functional change intended. Cc: Chris Healy <[email protected]> Cc: Kyle McMartin <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Masahiro Yamada <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: linux-kernel <[email protected]> Signed-off-by: Andrey Smirnov <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
85 lines
2.2 KiB
C
85 lines
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Compact binary representation of ihex records. Some devices need their
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* firmware loaded in strange orders rather than a single big blob, but
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* actually parsing ihex-as-text within the kernel seems silly. Thus,...
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*/
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#ifndef __LINUX_IHEX_H__
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#define __LINUX_IHEX_H__
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#include <linux/types.h>
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#include <linux/firmware.h>
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#include <linux/device.h>
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/* Intel HEX files actually limit the length to 256 bytes, but we have
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drivers which would benefit from using separate records which are
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longer than that, so we extend to 16 bits of length */
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struct ihex_binrec {
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__be32 addr;
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__be16 len;
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uint8_t data[0];
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} __attribute__((packed));
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static inline uint16_t ihex_binrec_size(const struct ihex_binrec *p)
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{
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return be16_to_cpu(p->len) + sizeof(*p);
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}
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/* Find the next record, taking into account the 4-byte alignment */
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static inline const struct ihex_binrec *
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__ihex_next_binrec(const struct ihex_binrec *rec)
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{
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const void *p = rec;
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return p + ALIGN(ihex_binrec_size(rec), 4);
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}
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static inline const struct ihex_binrec *
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ihex_next_binrec(const struct ihex_binrec *rec)
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{
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rec = __ihex_next_binrec(rec);
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return be16_to_cpu(rec->len) ? rec : NULL;
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}
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/* Check that ihex_next_binrec() won't take us off the end of the image... */
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static inline int ihex_validate_fw(const struct firmware *fw)
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{
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const struct ihex_binrec *end, *rec;
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rec = (const void *)fw->data;
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end = (const void *)&fw->data[fw->size - sizeof(*end)];
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for (; rec <= end; rec = __ihex_next_binrec(rec)) {
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/* Zero length marks end of records */
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if (rec == end && !be16_to_cpu(rec->len))
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return 0;
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}
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return -EINVAL;
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}
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/* Request firmware and validate it so that we can trust we won't
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* run off the end while reading records... */
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static inline int request_ihex_firmware(const struct firmware **fw,
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const char *fw_name,
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struct device *dev)
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{
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const struct firmware *lfw;
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int ret;
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ret = request_firmware(&lfw, fw_name, dev);
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if (ret)
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return ret;
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ret = ihex_validate_fw(lfw);
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if (ret) {
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dev_err(dev, "Firmware \"%s\" not valid IHEX records\n",
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fw_name);
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release_firmware(lfw);
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return ret;
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}
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*fw = lfw;
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return 0;
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}
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#endif /* __LINUX_IHEX_H__ */
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