[PATCH] net/at91_ether: fix loading when macb is compiled as a module

[PATCH] net/at91_ether: fix loading when macb is compiled as a module

[Gilles Chanteperdrix]

The at91_ether driver depends on symbols defined in the macb driver.

Currently, when compiling both at91_ether and macb as module, starting
the at91_ether module fails, because the macb module can not be loaded
with a macb interface.

Avoid this issue by getting the macb module initialization routine to
always return 0, even when no macb device is detected.

Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
---
 drivers/net/ethernet/cadence/macb.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 4d9fc05..f70228c 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -2327,7 +2327,20 @@ static struct platform_driver macb_driver = {
 	},
 };
 
-module_platform_driver_probe(macb_driver, macb_probe);
+static bool found;
+static int __init macb_driver_init(void)
+{
+	found = platform_driver_probe(&macb_driver, macb_probe) == 0;
+	return 0;
+}
+module_init(macb_driver_init);
+
+static void __exit macb_driver_exit(void)
+{
+	if (found)
+		platform_driver_unregister(&macb_driver);
+}
+module_exit(macb_driver_exit);
 
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Cadence MACB/GEM Ethernet driver");
-- 
1.7.10.4

Re: [PATCH] net/at91_ether: fix loading when macb is compiled as a module

[David Miller]

From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Date: Sun, 16 Nov 2014 19:05:06 +0100

> The at91_ether driver depends on symbols defined in the macb driver.
> 
> Currently, when compiling both at91_ether and macb as module, starting
> the at91_ether module fails, because the macb module can not be loaded
> with a macb interface.
> 
> Avoid this issue by getting the macb module initialization routine to
> always return 0, even when no macb device is detected.
> 
> Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>

This is not acceptable, sorry.

This means the module stays in memory even if nobody has a real use
for it.

You'll need to find another solution, and I'll say in passing that this
was very poorly designed and that's why the problem exists.

Re: [PATCH] net/at91_ether: fix loading when macb is compiled as a module

[Gilles Chanteperdrix]

On Sun, Nov 16, 2014 at 01:53:02PM -0500, David Miller wrote:
> From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
> Date: Sun, 16 Nov 2014 19:05:06 +0100
> 
> > The at91_ether driver depends on symbols defined in the macb driver.
> > 
> > Currently, when compiling both at91_ether and macb as module, starting
> > the at91_ether module fails, because the macb module can not be loaded
> > with a macb interface.
> > 
> > Avoid this issue by getting the macb module initialization routine to
> > always return 0, even when no macb device is detected.
> > 
> > Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
> 
> This is not acceptable, sorry.
> 
> This means the module stays in memory even if nobody has a real use
> for it.
> 
> You'll need to find another solution, and I'll say in passing that this
> was very poorly designed and that's why the problem exists.
> 

Ok, I see multiple possible other fixes:
- inline the shared functions in the macb.h driver or move them to a
library, this effectively means duplication, but who is going to
enable both drivers anyway?
- when both drivers are compiled as module, make one module
containing both drivers say at91+macb.ko
- modify the code I posted so that it only keeps the macb driver
loaded without macb device if IS_ENABLED(CONFIG_ARM_AT91_ETHER)
and probably many others I do not see.

I just do not know which one you would find acceptable.

Regards.

-- 
					    Gilles.