Re: [PATCH 01/19] bus/cdx: add the cdx bus driver

On Tue, Jan 17, 2023 at 07:11:33PM +0530, Nipun Gupta wrote:

Introduce AMD CDX bus, which provides a mechanism for scanning
and probing CDX devices. These devices are memory mapped on
system bus for Application Processors(APUs).

CDX devices can be changed dynamically in the Fabric and CDX
bus interacts with CDX controller to rescan the bus and
rediscover the devices.

Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
Signed-off-by: Tarak Reddy <redacted>

First off, very nice job, I didn't find any obvious issues with this
integration into the driver core.

That being said, why do you want this in drivers/bus/?  Why not
drivers/cdx/ ?

One minor comment to make the code smaller:

+static int get_free_index(void)
+{
+	unsigned long id_map;
+	unsigned long mask;
+	int index = 0;
+
+	mask  = (1UL << MAX_CDX_CONTROLLERS) - 1;
+retry:
+	id_map = cdx_controller_id_map[0];
+	if ((id_map & mask) == mask)
+		return -ENOSPC;
+
+	index = ffz(id_map);
+	if (index >= MAX_CDX_CONTROLLERS)
+		return -ENOSPC;
+
+	if (test_and_set_bit(index, &cdx_controller_id_map[0]))
+		goto retry;
+
+	return index;
+}

Why not just use the idr/ida structure instead?  That will handle all of
that logic for you and get rid of your bit twiddling.

+/**
+ * struct cdx_dev_params - CDX device parameters
+ * @cdx: CDX controller associated with the device
+ * @parent: Associated CDX controller
+ * @vendor: Vendor ID for CDX device
+ * @device: Device ID for CDX device
+ * @bus_num: Bus number for this CDX device
+ * @dev_num: Device number for this device
+ * @res: array of MMIO region entries
+ * @res_count: number of valid MMIO regions
+ * @req_id: Requestor ID associated with CDX device
+ */
+struct cdx_dev_params {
+	struct cdx_controller *cdx;
+	u16 vendor;
+	u16 device;

Are these in little endian format in memory?  Or native?  Or something
else?

thanks,

greg k-h

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel