我正在研究iso安装程序。出于某些奇怪的原因，此安装程序必须选择sda作为要在其中安装os的磁盘。因此，安装程序本身没有解决方法，我想修改内核以归档目标。
AFAIK，usb和sata / ata设备都可以是sda，因为它们都可以与scsi通讯，并且scsi驱动程序会将scsi设备重新识别为sda..z。因此，将USB设备重新识别为sda并不奇怪。作为内核新手，我不知道大型内核代码库的背后是什么。例如，内核如何将scsi设备注册为sda（好的，我只能找到函数sd_format_disk_name
/**
* sd_format_disk_name - format disk name
* @prefix: name prefix - ie. "sd" for SCSI disks
* @index: index of the disk to format name for
* @buf: output buffer
* @buflen: length of the output buffer
*
* SCSI disk names starts at sda. The 26th device is sdz and the
* 27th is sdaa. The last one for two lettered suffix is sdzz
* which is followed by sdaaa.
*
* This is basically 26 base counting with one extra 'nil' entry
* at the beginning from the second digit on and can be
* determined using similar method as 26 base conversion with the
* index shifted -1 after each digit is computed.
*
* CONTEXT:
* Don't care.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
static int sd_format_disk_name(char *prefix, int index, char *buf, int buflen)
{
const int base = 'z' - 'a' + 1;
char *begin = buf + strlen(prefix);
char *end = buf + buflen;
char *p;
int unit;
p = end - 1;
*p = '\0';
unit = base;
do {
if (p == begin)
return -EINVAL;
*--p = 'a' + (index % unit);
index = (index / unit) - 1;
} while (index >= 0);
memmove(begin, p, end - p);
memcpy(buf, prefix, strlen(prefix));
return 0;
}
在sd_probe中被称为
/**
* sd_probe - called during driver initialization and whenever a
* new scsi device is attached to the system. It is called once
* for each scsi device (not just disks) present.
* @dev: pointer to device object
*
* Returns 0 if successful (or not interested in this scsi device
* (e.g. scanner)); 1 when there is an error.
*
* Note: this function is invoked from the scsi mid-level.
* This function sets up the mapping between a given
* <host,channel,id,lun> (found in sdp) and new device name
* (e.g. /dev/sda). More precisely it is the block device major
* and minor number that is chosen here.
*
* Assume sd_probe is not re-entrant (for time being)
* Also think about sd_probe() and sd_remove() running coincidentally.
**/
static int sd_probe(struct device *dev)
{
struct scsi_device *sdp = to_scsi_device(dev);
struct scsi_disk *sdkp;
struct gendisk *gd;
int index;
int error;
scsi_autopm_get_device(sdp);
error = -ENODEV;
if (sdp->type != TYPE_DISK && sdp->type != TYPE_MOD && sdp->type != TYPE_RBC)
goto out;
SCSI_LOG_HLQUEUE(3, sdev_printk(KERN_INFO, sdp,
"sd_probe\n"));
error = -ENOMEM;
sdkp = kzalloc(sizeof(*sdkp), GFP_KERNEL);
if (!sdkp)
goto out;
gd = alloc_disk(SD_MINORS);
if (!gd)
goto out_free;
do {
if (!ida_pre_get(&sd_index_ida, GFP_KERNEL))
goto out_put;
spin_lock(&sd_index_lock);
error = ida_get_new(&sd_index_ida, &index);
spin_unlock(&sd_index_lock);
} while (error == -EAGAIN);
if (error) {
sdev_printk(KERN_WARNING, sdp, "sd_probe: memory exhausted.\n");
goto out_put;
}
error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);
if (error) {
sdev_printk(KERN_WARNING, sdp, "SCSI disk (sd) name length exceeded.\n");
goto out_free_index;
}
sdkp->device = sdp;
sdkp->driver = &sd_template;
sdkp->disk = gd;
sdkp->index = index;
atomic_set(&sdkp->openers, 0);
atomic_set(&sdkp->device->ioerr_cnt, 0);
if (!sdp->request_queue->rq_timeout) {
if (sdp->type != TYPE_MOD)
blk_queue_rq_timeout(sdp->request_queue, SD_TIMEOUT);
else
blk_queue_rq_timeout(sdp->request_queue,
SD_MOD_TIMEOUT);
}
device_initialize(&sdkp->dev);
sdkp->dev.parent = dev;
sdkp->dev.class = &sd_disk_class;
dev_set_name(&sdkp->dev, "%s", dev_name(dev));
error = device_add(&sdkp->dev);
if (error)
goto out_free_index;
get_device(dev);
dev_set_drvdata(dev, sdkp);
get_device(&sdkp->dev); /* prevent release before async_schedule */
async_schedule_domain(sd_probe_async, sdkp, &scsi_sd_probe_domain);
return 0;
out_free_index:
spin_lock(&sd_index_lock);
ida_remove(&sd_index_ida, index);
spin_unlock(&sd_index_lock);
out_put:
put_disk(gd);
out_free:
kfree(sdkp);
out:
scsi_autopm_put_device(sdp);
return error;
}
可悲的是，这两个功能远远不能满足我的要求。
问题：