Re: Requirements for a shutdown function?

On 05/09/2017 09:58 AM, Timur Tabi wrote:

I'm trying to add a platform_driver.shutdown function to my Ethernet driver
(drivers/net/ethernet/qualcomm/emac/*), but I can't find any definitive
information as to what a network driver shutdown callback is supposed to do.
 I also don't know what testcase I should use to verify that my function is
working.

A good test case for exercising a .shutdown() function is kexec'ing a
new kernel for instance.

I see only four instances of a platform_driver.shutdown function in
drivers/net/ethernet:

$ git grep -A 20 -w platform_driver | grep '\.shutdown'
apm/xgene-v2/main.c-	.shutdown = xge_shutdown,
apm/xgene/xgene_enet_main.c-	.shutdown = xgene_enet_shutdown,
marvell/mv643xx_eth.c-	.shutdown	= mv643xx_eth_shutdown,
marvell/pxa168_eth.c-	.shutdown = pxa168_eth_shutdown,

(Other shutdown functions are for pci_driver.shutdown).

For the xgene drivers, the shutdown function just calls the 'remove'
function.  Isn't that overkill?  Why bother with a shutdown function if it's
just the same thing as removing the driver outright?

Yes, that appears unnecessary.

mv643xx_eth_shutdown() seems more reasonable.  All it does is halt the TX
and RX queues.

pxa168_eth_shutdown() is a little more heavyweight: halts the queues, and
stops the DMA and calls phy_stop().

Can anyone help me figure out what my driver really should do?

You should put your HW in a state where it won't be doing DMA, or have
any adverse side effects to the system, putting it in a low power state
is also a good approach.
-- 
Florian