block: Allow t10-pi to be modular

Currently t10-pi can only be built into the block layer which via
crc-t10dif pulls in a whole chunk of the Crypto API.  In fact all
users of t10-pi work as modules and there is no reason for it to
always be built-in.

This patch adds a new hidden option for t10-pi that is selected
automatically based on BLK_DEV_INTEGRITY and whether the users
of t10-pi are built-in or not.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/Kconfig

@@ -66,7 +66,6 @@ config BLK_DEV_BSGLIB
 
 config BLK_DEV_INTEGRITY
 	bool "Block layer data integrity support"
-	select CRC_T10DIF if BLK_DEV_INTEGRITY
 	---help---
 	Some storage devices allow extra information to be
 	stored/retrieved to help protect the data.  The block layer
@@ -77,6 +76,11 @@ config BLK_DEV_INTEGRITY
 	T10/SCSI Data Integrity Field or the T13/ATA External Path
 	Protection.  If in doubt, say N.
 
+config BLK_DEV_INTEGRITY_T10
+	tristate
+	depends on BLK_DEV_INTEGRITY
+	select CRC_T10DIF
+
 config BLK_DEV_ZONED
 	bool "Zoned block device support"
 	select MQ_IOSCHED_DEADLINE

block/Makefile

@@ -27,7 +27,8 @@ obj-$(CONFIG_IOSCHED_BFQ)	+= bfq.o
 
 obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
 obj-$(CONFIG_BLK_CMDLINE_PARSER)	+= cmdline-parser.o
-obj-$(CONFIG_BLK_DEV_INTEGRITY) += bio-integrity.o blk-integrity.o t10-pi.o
+obj-$(CONFIG_BLK_DEV_INTEGRITY) += bio-integrity.o blk-integrity.o
+obj-$(CONFIG_BLK_DEV_INTEGRITY_T10)	+= t10-pi.o
 obj-$(CONFIG_BLK_MQ_PCI)	+= blk-mq-pci.o
 obj-$(CONFIG_BLK_MQ_VIRTIO)	+= blk-mq-virtio.o
 obj-$(CONFIG_BLK_MQ_RDMA)	+= blk-mq-rdma.o

block/t10-pi.c

@@ -7,6 +7,7 @@
 #include <linux/t10-pi.h>
 #include <linux/blkdev.h>
 #include <linux/crc-t10dif.h>
+#include <linux/module.h>
 #include <net/checksum.h>
 
 typedef __be16 (csum_fn) (void *, unsigned int);
@@ -280,3 +281,5 @@ const struct blk_integrity_profile t10_pi_type3_ip = {
 	.complete_fn		= t10_pi_type3_complete,
 };
 EXPORT_SYMBOL(t10_pi_type3_ip);
+
+MODULE_LICENSE("GPL");

drivers/nvme/host/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
 config NVME_CORE
 	tristate
+	select BLK_DEV_INTEGRITY_T10 if BLK_DEV_INTEGRITY
 
 config BLK_DEV_NVME
 	tristate "NVM Express block device"

drivers/scsi/Kconfig

@@ -68,6 +68,7 @@ comment "SCSI support type (disk, tape, CD-ROM)"
 config BLK_DEV_SD
 	tristate "SCSI disk support"
 	depends on SCSI
+	select BLK_DEV_INTEGRITY_T10 if BLK_DEV_INTEGRITY
 	---help---
 	  If you want to use SCSI hard disks, Fibre Channel disks,
 	  Serial ATA (SATA) or Parallel ATA (PATA) hard disks,