The net fixed phy driver does not require the creation of a platform
device. Originally, this approach was chosen for simplicity when the
driver was first implemented.

With the introduction of the lightweight faux device interface, we now
have a more appropriate alternative. Migrate the driver to utilize the
faux bus, given that the platform device it previously created was not
a real one anyway. This will simplify the code, reducing its footprint
while maintaining functionality.

Cc: Andrew Lunn <andrew@lunn.ch>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 drivers/net/phy/fixed_phy.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/phy/fixed_phy.c b/drivers/net/phy/fixed_phy.c
index aef739c20ac4d5a271465a677a85ef7c18cfce70..ee7831a9849b3728ca9c541da35d17e089985da2 100644
--- a/drivers/net/phy/fixed_phy.c
+++ b/drivers/net/phy/fixed_phy.c
@@ -10,7 +10,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/platform_device.h>
+#include <linux/device/faux.h>
 #include <linux/list.h>
 #include <linux/mii.h>
 #include <linux/phy.h>
@@ -40,7 +40,7 @@ struct fixed_phy {
 	struct gpio_desc *link_gpiod;
 };
 
-static struct platform_device *pdev;
+static struct faux_device *fdev;
 static struct fixed_mdio_bus platform_fmb = {
 	.phys = LIST_HEAD_INIT(platform_fmb.phys),
 };
@@ -337,9 +337,9 @@ static int __init fixed_mdio_bus_init(void)
 	struct fixed_mdio_bus *fmb = &platform_fmb;
 	int ret;
 
-	pdev = platform_device_register_simple("Fixed MDIO bus", 0, NULL, 0);
-	if (IS_ERR(pdev))
-		return PTR_ERR(pdev);
+	fdev = faux_device_create("Fixed MDIO bus", NULL, NULL);
+	if (!fdev)
+		return -ENODEV;
 
 	fmb->mii_bus = mdiobus_alloc();
 	if (fmb->mii_bus == NULL) {
@@ -350,7 +350,7 @@ static int __init fixed_mdio_bus_init(void)
 	snprintf(fmb->mii_bus->id, MII_BUS_ID_SIZE, "fixed-0");
 	fmb->mii_bus->name = "Fixed MDIO Bus";
 	fmb->mii_bus->priv = fmb;
-	fmb->mii_bus->parent = &pdev->dev;
+	fmb->mii_bus->parent = &fdev->dev;
 	fmb->mii_bus->read = &fixed_mdio_read;
 	fmb->mii_bus->write = &fixed_mdio_write;
 	fmb->mii_bus->phy_mask = ~0;
@@ -364,7 +364,7 @@ static int __init fixed_mdio_bus_init(void)
 err_mdiobus_alloc:
 	mdiobus_free(fmb->mii_bus);
 err_mdiobus_reg:
-	platform_device_unregister(pdev);
+	faux_device_destroy(fdev);
 	return ret;
 }
 module_init(fixed_mdio_bus_init);
@@ -376,7 +376,7 @@ static void __exit fixed_mdio_bus_exit(void)
 
 	mdiobus_unregister(fmb->mii_bus);
 	mdiobus_free(fmb->mii_bus);
-	platform_device_unregister(pdev);
+	faux_device_destroy(fdev);
 
 	list_for_each_entry_safe(fp, tmp, &fmb->phys, node) {
 		list_del(&fp->node);

-- 
2.34.1

On Mon, Mar 17, 2025 at 10:13:19AM +0000, Sudeep Holla wrote:
> The net fixed phy driver does not require the creation of a platform
> device. Originally, this approach was chosen for simplicity when the
> driver was first implemented.
> 
> With the introduction of the lightweight faux device interface, we now
> have a more appropriate alternative. Migrate the driver to utilize the
> faux bus, given that the platform device it previously created was not
> a real one anyway. This will simplify the code, reducing its footprint
> while maintaining functionality.
> 
> Cc: Andrew Lunn <andrew@lunn.ch>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/net/phy/fixed_phy.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)

8 insertions, 8 deletions. How does this reduce its footprint?

Seems like pointless churn to me. Unless there is a real advantage to
faux bus you are not enumerating in your commit message.

	Andrew

On Mon, Mar 17, 2025 at 01:29:31PM +0100, Andrew Lunn wrote:
> On Mon, Mar 17, 2025 at 10:13:19AM +0000, Sudeep Holla wrote:
> > The net fixed phy driver does not require the creation of a platform
> > device. Originally, this approach was chosen for simplicity when the
> > driver was first implemented.
> > 
> > With the introduction of the lightweight faux device interface, we now
> > have a more appropriate alternative. Migrate the driver to utilize the
> > faux bus, given that the platform device it previously created was not
> > a real one anyway. This will simplify the code, reducing its footprint
> > while maintaining functionality.
> > 
> > Cc: Andrew Lunn <andrew@lunn.ch>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: netdev@vger.kernel.org
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > ---
> >  drivers/net/phy/fixed_phy.c | 16 ++++++++--------
> >  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> 8 insertions, 8 deletions. How does this reduce its footprint?
>

I meant the use of struct faux_device vs struct platform_device. Yes
it is not a big deal.

> Seems like pointless churn to me. Unless there is a real advantage to
> faux bus you are not enumerating in your commit message.
> 

Greg has answered that, so will skip.

-- 
Regards,
Sudeep

On Mon, Mar 17, 2025 at 01:29:31PM +0100, Andrew Lunn wrote:
> On Mon, Mar 17, 2025 at 10:13:19AM +0000, Sudeep Holla wrote:
> > The net fixed phy driver does not require the creation of a platform
> > device. Originally, this approach was chosen for simplicity when the
> > driver was first implemented.
> > 
> > With the introduction of the lightweight faux device interface, we now
> > have a more appropriate alternative. Migrate the driver to utilize the
> > faux bus, given that the platform device it previously created was not
> > a real one anyway. This will simplify the code, reducing its footprint
> > while maintaining functionality.
> > 
> > Cc: Andrew Lunn <andrew@lunn.ch>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: netdev@vger.kernel.org
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > ---
> >  drivers/net/phy/fixed_phy.c | 16 ++++++++--------
> >  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> 8 insertions, 8 deletions. How does this reduce its footprint?
> 
> Seems like pointless churn to me. Unless there is a real advantage to
> faux bus you are not enumerating in your commit message.

It stops the abuse of using a platform device for something that is NOT
a platform device.  This file should have never used a platform device
for this in the first place, and this change is fixing that design bug.

thanks,

greg k-h