tpm: make all 'class' structures const

Now that the driver core allows for struct class to be in read-only
memory, making all 'class' structures to be declared at build time
placing them into read-only memory, instead of having to be dynamically
allocated at load time.

Cc: Peter Huewe <peterhuewe@gmx.de>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-integrity@vger.kernel.org
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/20230620144642.584926-2-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/tpm/tpm-chip.c

@@ -28,8 +28,13 @@
 DEFINE_IDR(dev_nums_idr);
 static DEFINE_MUTEX(idr_lock);
 
-struct class *tpm_class;
-struct class *tpmrm_class;
+const struct class tpm_class = {
+	.name = "tpm",
+	.shutdown_pre = tpm_class_shutdown,
+};
+const struct class tpmrm_class = {
+	.name = "tmprm",
+};
 dev_t tpm_devt;
 
 static int tpm_request_locality(struct tpm_chip *chip)
@@ -336,7 +341,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
 
 	device_initialize(&chip->dev);
 
-	chip->dev.class = tpm_class;
+	chip->dev.class = &tpm_class;
 	chip->dev.release = tpm_dev_release;
 	chip->dev.parent = pdev;
 	chip->dev.groups = chip->groups;

drivers/char/tpm/tpm-interface.c

@@ -476,18 +476,15 @@ static int __init tpm_init(void)
 {
 	int rc;
 
-	tpm_class = class_create("tpm");
-	if (IS_ERR(tpm_class)) {
+	rc = class_register(&tpm_class);
+	if (rc) {
 		pr_err("couldn't create tpm class\n");
-		return PTR_ERR(tpm_class);
+		return rc;
 	}
 
-	tpm_class->shutdown_pre = tpm_class_shutdown;
-
-	tpmrm_class = class_create("tpmrm");
-	if (IS_ERR(tpmrm_class)) {
+	rc = class_register(&tpmrm_class);
+	if (rc) {
 		pr_err("couldn't create tpmrm class\n");
-		rc = PTR_ERR(tpmrm_class);
 		goto out_destroy_tpm_class;
 	}
 
@@ -508,9 +505,9 @@ static int __init tpm_init(void)
 out_unreg_chrdev:
 	unregister_chrdev_region(tpm_devt, 2 * TPM_NUM_DEVICES);
 out_destroy_tpmrm_class:
-	class_destroy(tpmrm_class);
+	class_unregister(&tpmrm_class);
 out_destroy_tpm_class:
-	class_destroy(tpm_class);
+	class_unregister(&tpm_class);
 
 	return rc;
 }
@@ -518,8 +515,8 @@ static int __init tpm_init(void)
 static void __exit tpm_exit(void)
 {
 	idr_destroy(&dev_nums_idr);
-	class_destroy(tpm_class);
-	class_destroy(tpmrm_class);
+	class_unregister(&tpm_class);
+	class_unregister(&tpmrm_class);
 	unregister_chrdev_region(tpm_devt, 2*TPM_NUM_DEVICES);
 	tpm_dev_common_exit();
 }

drivers/char/tpm/tpm.h

@@ -230,8 +230,8 @@ enum tpm2_pt_props {
  * compiler warnings about stack frame size. */
 #define TPM_MAX_RNG_DATA	128
 
-extern struct class *tpm_class;
-extern struct class *tpmrm_class;
+extern const struct class tpm_class;
+extern const struct class tpmrm_class;
 extern dev_t tpm_devt;
 extern const struct file_operations tpm_fops;
 extern const struct file_operations tpmrm_fops;

drivers/char/tpm/tpm2-space.c

@@ -606,7 +606,7 @@ int tpm_devs_add(struct tpm_chip *chip)
 
 	device_initialize(&chip->devs);
 	chip->devs.parent = chip->dev.parent;
-	chip->devs.class = tpmrm_class;
+	chip->devs.class = &tpmrm_class;
 
 	/*
 	 * Get extra reference on main device to hold on behalf of devs.