partition: DOS: Add parameter for the NT disk Signature
The NT disk Signature is a unique 32-bit value in the MBR allowing to identify a MSDOS partitioned disk. The signature can be used to specify the Linux rootfs. This patch adds support for the NT disk Signature in the form of a device parameter which can both be read and written. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
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@ -16,6 +16,8 @@
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#include <disks.h>
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#include <init.h>
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#include <asm/unaligned.h>
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#include <dma.h>
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#include <linux/err.h>
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#include "parser.h"
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@ -40,6 +42,74 @@ static int disk_guess_size(struct device_d *dev, struct partition_entry *table)
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return (int)size;
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}
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static void *read_mbr(struct block_device *blk)
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{
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void *buf = dma_alloc(SECTOR_SIZE);
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int ret;
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ret = block_read(blk, buf, 0, 1);
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if (ret) {
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free(buf);
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return NULL;
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}
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return buf;
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}
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static int write_mbr(struct block_device *blk, void *buf)
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{
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int ret;
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ret = block_write(blk, buf, 0, 1);
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if (ret)
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return ret;
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return block_flush(blk);
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}
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struct disk_signature_priv {
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uint32_t signature;
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struct block_device *blk;
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};
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static int dos_set_disk_signature(struct param_d *p, void *_priv)
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{
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struct disk_signature_priv *priv = _priv;
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struct block_device *blk = priv->blk;
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void *buf;
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__le32 *disksigp;
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int ret;
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buf = read_mbr(blk);
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if (!buf)
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return -EIO;
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disksigp = buf + 0x1b8;
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*disksigp = cpu_to_le32(priv->signature);
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ret = write_mbr(blk, buf);
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free(buf);
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return ret;
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}
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static int dos_get_disk_signature(struct param_d *p, void *_priv)
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{
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struct disk_signature_priv *priv = _priv;
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struct block_device *blk = priv->blk;
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void *buf;
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buf = read_mbr(blk);
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if (!buf)
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return -EIO;
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priv->signature = le32_to_cpup((__le32 *)(buf + 0x1b8));
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return 0;
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}
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/**
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* Check if a DOS like partition describes this block device
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* @param blk Block device to register to
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@ -55,6 +125,7 @@ static void dos_partition(void *buf, struct block_device *blk,
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struct partition pentry;
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uint8_t *buffer = buf;
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int i;
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struct disk_signature_priv *dsp;
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table = (struct partition_entry *)&buffer[446];
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@ -74,6 +145,23 @@ static void dos_partition(void *buf, struct block_device *blk,
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dev_dbg(blk->dev, "Skipping empty partition %d\n", i);
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}
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}
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dsp = xzalloc(sizeof(*dsp));
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dsp->blk = blk;
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/*
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* This parameter contains the NT disk signature. This allows to
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* to specify the Linux rootfs using the following syntax:
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*
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* root=PARTUUID=ssssssss-pp
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*
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* where ssssssss is a zero-filled hex representation of the 32-bit
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* signature and pp is a zero-filled hex representation of the 1-based
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* partition number.
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*/
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dev_add_param_int(blk->dev, "nt_signature",
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dos_set_disk_signature, dos_get_disk_signature,
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&dsp->signature, "%08x", dsp);
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}
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static struct partition_parser dos = {
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