linux-kernel - Re: [RFC PATCH] net: phy/mdio: enable mmd indirect access through phy_mii

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Date:   Tue, 2 Nov 2021 21:12:29 +0200
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
CC:     Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        <linux-kernel@...r.kernel.org>,
        Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [RFC PATCH] net: phy/mdio: enable mmd indirect access through
 phy_mii_ioctl()



On 02/11/2021 20:37, Grygorii Strashko wrote:
> Hi Russell, Andrew,
> 
> Thanks a lot for you comments.
> 
> On 02/11/2021 19:41, Russell King (Oracle) wrote:
>> On Tue, Nov 02, 2021 at 07:19:46PM +0200, Grygorii Strashko wrote:
>>> It would require MDIO bus lock, which is not a solution,
>>> or some sort of batch processing, like for mmd:
>>>   w reg1 val1
>>>   w reg2 val2
>>>   w reg1 val3
>>>   r reg2
>>>
>>> What Kernel interface do you have in mind?
>>
>> That is roughly what I was thinking, but Andrew has basically said no
>> to it.
>>
>>> Sry, but I have to note that demand for this become terribly high, min two pings in months
>>
>> Feel free to continue demanding it, but it seems that at least two of
>> the phylib maintainers are in agreement that providing generic
>> emulation of C45 accesses in kernel space is just not going to happen.
>>
> 
> not ready to give up.
> 
> One more idea how about mdiobus_get_phy(), so we can search for PHY and
> if present try to use proper API phy_read/phy_write_mmd?
> 
> 

smth like below
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index a3bfb156c83d..8ebe59b5647d 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -285,6 +285,7 @@ int phy_mii_ioctl(struct phy_device *phydev, struct ifreq *ifr, int cmd)
         u16 val = mii_data->val_in;
         bool change_autoneg = false;
         int prtad, devad;
+       struct phy_device *phydev_rq = phydev;
  
         switch (cmd) {
         case SIOCGMIIPHY:
@@ -300,8 +301,18 @@ int phy_mii_ioctl(struct phy_device *phydev, struct ifreq *ifr, int cmd)
                         prtad = mii_data->phy_id;
                         devad = mii_data->reg_num;
                 }
-               mii_data->val_out = mdiobus_read(phydev->mdio.bus, prtad,
-                                                devad);
+
+               if (prtad != phydev->mdio.addr)
+                       phydev_rq = mdiobus_get_phy(phydev->mdio.bus, prtad);
+
+               if (!phydev_rq) {
+                       mii_data->val_out = mdiobus_read(phydev->mdio.bus, prtad, devad);
+               } else if (mdio_phy_id_is_c45(mii_data->phy_id) && !phydev->is_c45) {
+                       mii_data->val_out = phy_read_mmd(phydev_rq, mdio_phy_id_devad(mii_data->phy_id), mii_data->reg_num);
+               } else {
+                       mii_data->val_out = phy_read(phydev_rq, mii_data->reg_num);
+               }
+
                 return 0;
  
         case SIOCSMIIREG:

-- 
Best regards,
grygorii