staging: kpc2000: use IDA to assign card numbers.

Previously the next card number was assigned from a static int local
variable.  Replaced it with an IDA.  Avoids the assignment of ever-
increasing card-numbers by allowing them to be reused.

Updated TODO.

Corrected format-specifier for unsigned pcard->card_num.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/kpc2000/TODO

 - the kpc_spi driver doesn't seem to let multiple transactions (to different instances of the core) happen in parallel...
 - The kpc_i2c driver is a hot mess, it should probably be cleaned up a ton.  It functions against current hardware though.
-- pcard->card_num in kp2000_pcie_probe() is a global variable and needs atomic / locking / something better.
 - would be nice if the AIO fileops in kpc_dma could be made to work
     - probably want to add a CONFIG_ option to control compilation of the AIO functions
 - if the AIO fileops in kpc_dma start working, next would be making iov_count > 1 work too

drivers/staging/kpc2000/kpc2000/core.c

 // SPDX-License-Identifier: GPL-2.0+
 #include <linux/kernel.h>
+#include <linux/idr.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/pci.h>
@@ -25,6 +26,8 @@
 #include "pcie.h"
 #include "uapi.h"
 
+static DEFINE_IDA(card_num_ida);
+
 /*******************************************************
  * SysFS Attributes
  ******************************************************/
@@ -388,7 +391,6 @@ static int kp2000_pcie_probe(struct pci_dev *pdev,
 {
 	int err = 0;
 	struct kp2000_device *pcard;
-	static int card_count = 1;
 	int rv;
 	unsigned long reg_bar_phys_addr;
 	unsigned long reg_bar_phys_len;
@@ -414,9 +416,14 @@ static int kp2000_pcie_probe(struct pci_dev *pdev,
 	/*
 	 * Step 2: Initialize trivial pcard elements
 	 */
-	pcard->card_num = card_count;
-	card_count++;
-	scnprintf(pcard->name, 16, "kpcard%d", pcard->card_num);
+	err = ida_simple_get(&card_num_ida, 1, INT_MAX, GFP_KERNEL);
+	if (err < 0) {
+		dev_err(&pdev->dev, "probe: failed to get card number (%d)\n",
+			err);
+		goto out2;
+	}
+	pcard->card_num = err;
+	scnprintf(pcard->name, 16, "kpcard%u", pcard->card_num);
 
 	mutex_init(&pcard->sem);
 	mutex_lock(&pcard->sem);
@@ -630,6 +637,8 @@ static int kp2000_pcie_probe(struct pci_dev *pdev,
 	pci_disable_device(pcard->pdev);
 out3:
 	mutex_unlock(&pcard->sem);
+	ida_simple_remove(&card_num_ida, pcard->card_num);
+out2:
 	kfree(pcard);
 	return err;
 }
@@ -663,6 +672,7 @@ static void kp2000_pcie_remove(struct pci_dev *pdev)
 	pci_disable_device(pcard->pdev);
 	pci_set_drvdata(pdev, NULL);
 	mutex_unlock(&pcard->sem);
+	ida_simple_remove(&card_num_ida, pcard->card_num);
 	kfree(pcard);
 }
 
@@ -698,6 +708,7 @@ static void __exit  kp2000_pcie_exit(void)
 {
 	pci_unregister_driver(&kp2000_driver_inst);
 	class_destroy(kpc_uio_class);
+	ida_destroy(&card_num_ida);
 }
 module_exit(kp2000_pcie_exit);