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s390/dasd: Add defines for the Extended Address Volume track address

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The track address of an Extended Address Volume (more than 65520
cylinders) carries the high cylinder bits that do not fit the 16-bit cyl
field in the upper part of the head field. set_ch_t() open-codes the
corresponding shifts; name them so the encoding is explicit and can be
reused.

No functional change.

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://patch.msgid.link/20260805111612.1285190-8-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Stefan Haberland
2026-08-05 13:16:00 +02:00
committed by Jens Axboe
parent feea12d1cd
commit 1edac73fa2
2 changed files with 10 additions and 2 deletions
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4
drivers/s390/block/dasd_eckd.c
View File

@@ -199,8 +199,8 @@ recs_per_track(struct dasd_eckd_characteristics * rdc,
static void set_ch_t(struct ch_t *geo, __u32 cyl, __u8 head)
{
geo->cyl = (__u16) cyl;
geo->head = cyl >> 16;
geo->head <<= 4;
geo->head = cyl >> DASD_EAV_CYL_HI_SHIFT;
geo->head <<= DASD_EAV_HEAD_HI_SHIFT;
geo->head |= head;
}

8
drivers/s390/block/dasd_eckd.h
View File

@@ -146,6 +146,14 @@ struct eckd_count {
__u16 dl;
} __attribute__ ((packed));
/*
* Extended Address Volume track address: the head field carries the actual
* head in its low-order 4 bits; the cylinder bits that do not fit the 16-bit
* cyl field are shifted in just above them.
*/
#define DASD_EAV_CYL_HI_SHIFT 16 /* cylinder bits beyond the 16-bit cyl field */
#define DASD_EAV_HEAD_HI_SHIFT 4 /* head occupies the low-order 4 bits of head */
struct ch_t {
__u16 cyl;
__u16 head;