ata: make "libata.force" kernel parameter optional

Add ATA_FORCE config option (visible only if EXPERT config
option is enabled) and make "libata.force" kernel parameter
optional.

Code size savings on m68k arch using (modified) atari_defconfig:

   text    data     bss     dec     hex filename
w/ CONFIG_ATA_FORCE=y:
  31983     572      40   32595    7f53 drivers/ata/libata-core.o
w/ CONFIG_ATA_FROCE=n:
  28958     316      32   29306    727a drivers/ata/libata-core.o
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/ata/Kconfig

@@ -51,6 +51,22 @@ config ATA_VERBOSE_ERROR
 
 	  If unsure, say Y.
 
+config ATA_FORCE
+	bool "\"libata.force=\" kernel parameter support" if EXPERT
+	default y
+	help
+	  This option adds support for "libata.force=" kernel parameter for
+	  forcing configuration settings.
+
+	  For further information, please read
+	  <file:Documentation/admin-guide/kernel-parameters.txt>.
+
+	  This option will enlarge the kernel by approx. 3KB. Disable it if
+	  kernel size is more important than ability to override the default
+	  configuration settings.
+
+	  If unsure, say Y.
+
 config ATA_ACPI
 	bool "ATA ACPI Support"
 	depends on ACPI

drivers/ata/libata-core.c

@@ -89,6 +89,7 @@ static unsigned long ata_dev_blacklisted(const struct ata_device *dev);
 
 atomic_t ata_print_id = ATOMIC_INIT(0);
 
+#ifdef CONFIG_ATA_FORCE
 struct ata_force_param {
 	const char	*name;
 	u8		cbl;
@@ -112,6 +113,7 @@ static char ata_force_param_buf[COMMAND_LINE_SIZE] __initdata;
 /* param_buf is thrown away after initialization, disallow read */
 module_param_string(force, ata_force_param_buf, sizeof(ata_force_param_buf), 0);
 MODULE_PARM_DESC(force, "Force ATA configurations including cable type, link speed and transfer mode (see Documentation/admin-guide/kernel-parameters.rst for details)");
+#endif
 
 static int atapi_enabled = 1;
 module_param(atapi_enabled, int, 0444);
@@ -303,6 +305,7 @@ struct ata_link *ata_dev_phys_link(struct ata_device *dev)
 	return ap->slave_link;
 }
 
+#ifdef CONFIG_ATA_FORCE
 /**
  *	ata_force_cbl - force cable type according to libata.force
  *	@ap: ATA port of interest
@@ -483,6 +486,11 @@ static void ata_force_horkage(struct ata_device *dev)
 			       fe->param.name);
 	}
 }
+#else
+static inline void ata_force_link_limits(struct ata_link *link) { }
+static inline void ata_force_xfermask(struct ata_device *dev) { }
+static inline void ata_force_horkage(struct ata_device *dev) { }
+#endif
 
 /**
  *	atapi_cmd_type - Determine ATAPI command type from SCSI opcode
@@ -6080,6 +6088,7 @@ int ata_platform_remove_one(struct platform_device *pdev)
 }
 EXPORT_SYMBOL_GPL(ata_platform_remove_one);
 
+#ifdef CONFIG_ATA_FORCE
 static int __init ata_parse_force_one(char **cur,
 				      struct ata_force_ent *force_ent,
 				      const char **reason)
@@ -6259,6 +6268,15 @@ static void __init ata_parse_force_param(void)
 	ata_force_tbl_size = idx;
 }
 
+static void ata_free_force_param(void)
+{
+	kfree(ata_force_tbl);
+}
+#else
+static inline void ata_parse_force_param(void) { }
+static inline void ata_free_force_param(void) { }
+#endif
+
 static int __init ata_init(void)
 {
 	int rc;
@@ -6267,7 +6285,7 @@ static int __init ata_init(void)
 
 	rc = ata_sff_init();
 	if (rc) {
-		kfree(ata_force_tbl);
+		ata_free_force_param();
 		return rc;
 	}
 
@@ -6291,7 +6309,7 @@ static void __exit ata_exit(void)
 	ata_release_transport(ata_scsi_transport_template);
 	libata_transport_exit();
 	ata_sff_exit();
-	kfree(ata_force_tbl);
+	ata_free_force_param();
 }
 
 subsys_initcall(ata_init);

drivers/ata/libata.h

@@ -37,7 +37,11 @@ extern int libata_noacpi;
 extern int libata_allow_tpm;
 extern const struct device_type ata_port_type;
 extern struct ata_link *ata_dev_phys_link(struct ata_device *dev);
+#ifdef CONFIG_ATA_FORCE
 extern void ata_force_cbl(struct ata_port *ap);
+#else
+static inline void ata_force_cbl(struct ata_port *ap) { }
+#endif
 extern u64 ata_tf_to_lba(const struct ata_taskfile *tf);
 extern u64 ata_tf_to_lba48(const struct ata_taskfile *tf);
 extern struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag);