Re: [RFC PATCH 01/11] phy: core add phy_set_netif_mode() api

Grygorii Strashko
2018-10-09T22:43:00Z

On 10/09/2018 12:22 AM, Kishon Vijay Abraham I wrote:
> Hi Grygorii,
>
> On Tuesday 09 October 2018 05:19 AM, Grygorii Strashko wrote:
>> Add new API phy_set_netif_mode(struct phy *phy, phy_interface_t mode) and
>> new PHY operation callback .set_netif_mode() which intended to be implemnte
>> by PHY drivers which supports Network interrfaces mode selection. Both
>> accepts phy_interface_t vlaue as input parameter.
>>
>> Cc: Kishon Vijay Abraham I <kishon@ti.com>
>> Cc: Tony Lindgren <tony@atomide.com>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
>> ---
>> drivers/phy/phy-core.c | 15 +++++++++++++++
>> include/linux/phy/phy.h | 12 ++++++++++++
>> 2 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
>> index 35fd38c..d9aba1a 100644
>> --- a/drivers/phy/phy-core.c
>> +++ b/drivers/phy/phy-core.c
>> @@ -377,6 +377,21 @@ int phy_set_mode(struct phy *phy, enum phy_mode mode)
>> }
>> EXPORT_SYMBOL_GPL(phy_set_mode);
>>
>> +int phy_set_netif_mode(struct phy *phy, phy_interface_t mode)
>> +{
>> + int ret;
>> +
>> + if (!phy || !phy->ops->set_netif_mode)
>> + return 0;
>> +
>> + mutex_lock(&phy->mutex);
>> + ret = phy->ops->set_netif_mode(phy, mode);
>> + mutex_unlock(&phy->mutex);
>> +
>> + return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(phy_set_netif_mode);
>
> We should try to add only generic PHY APIs and not subsystem specific APIs. In
> this case I think phy_set_mode should suffice.

This is what I've had in mind first, but all my guts argued against it after I've tried:

diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
index bc73d2b..961b156 100644
--- a/include/linux/phy/phy.h
+++ b/include/linux/phy/phy.h
@@ -41,6 +41,14 @@ enum phy_mode {
PHY_MODE_10GKR,
PHY_MODE_UFS_HS_A,
PHY_MODE_UFS_HS_B,
+ PHY_MODE_MODE_MII,
+ PHY_MODE_MODE_GMII,
+ PHY_MODE_MODE_SGMII,
+ PHY_MODE_MODE_RMII,
+ PHY_MODE_MODE_RGMII,
+ PHY_MODE_MODE_RGMII_ID,
+ PHY_MODE_MODE_RGMII_RXID,
+ PHY_MODE_MODE_RGMII_TXID,
};

above introduces ugly constants duplication and required every network phy driver
to maintain conversation table phy_interface_t -> enum phy_mode.
More over, if above change happens third time (first time PHY_MODE_SGMII/PHY_MODE_10GKR were added,
second - PHY_MODE_2500SGMII) it will never ends (there are ~15 more items only in phy_interface_t).
As result, enum phy_mode might became a un-maintainable monster.

So, as per above, and considering that Network subsystem is based on standards (phy_interface_t lists standard intf)
I've tried to add separate PHY API.

As an idea:
- seems it could be reasonable to introduce PHY_MODE_NETWORK (or PHY_MODE_ETHERNET) and
add generic phy_set_submode(struct phy *phy, long submode).

So, single functional PHY device can just use phy_set_submode() and
multi-functional devices (like serdes which can be muxed between PCIe, USB, NET), can use:

phy_set_mode(PHY_MODE_ETHERNET)
phy_set_submode(X);

Any way, if you still agree to just add new above phy_modes - i'll redo patches.

--
regards,
-grygorii