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Message-ID: <657b9999.5d0a0220.ec414.ed08@mx.google.com>
Date: Thu, 14 Dec 2023 18:29:28 +0100
From: Christian Marangi <ansuelsmth@...il.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
Andrew Lunn <andrew@...n.ch>,
Heiner Kallweit <hkallweit1@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Vladimir Oltean <olteanv@...il.com>,
David Epping <david.epping@...singlinkelectronics.com>,
Harini Katakam <harini.katakam@....com>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH v7 2/4] net: phy: extend PHY package API to
support multiple global address
On Thu, Dec 14, 2023 at 11:54:26PM +0000, Russell King (Oracle) wrote:
> On Thu, Dec 14, 2023 at 05:54:51PM +0100, Christian Marangi wrote:
> > What I don't like is the wrap check.
> >
> > But I wonder... Isn't it easier to have
> >
> > unsigned int addr = shared->base_addr + addr_offset;
> >
> > and check if >= PHY_MAC_ADDR?
> >
> > Everything is unsigned (so no negative case) and wrap is not possible as
> > nothing is downcasted.
>
> I'm afraid that I LOL'd at "wrap is not possible" ! Of course it's
> possible. Here's an example:
>
Yes I just think about it and I'm also LOLing at the "not possible"...
> shared->base_addr is 20
> addr_offset is ~0 (or -1 casted to an unsigned int)
> addr becomes 19
>
> How about:
>
> if (addr_offset >= PHY_MAX_ADDR)
> return -EIO;
>
> addr = shared->base_addr + addr_offset;
> if (addr >= PHY_MAX_ADDR)
> return -EIO;
>
> and then we could keep 'addr' as u8.
Ok just to make sure
static int phy_package_address(struct phy_device *phydev,
unsigned int addr_offset)
{
struct phy_package_shared *shared = phydev->shared;
unsigned int addr;
if (addr_offset >= PHY_MAX_ADDR)
return -EIO;
addr = shared->base_addr + addr_offset;
if (addr >= PHY_ADDR_MAX)
return -EIO;
/* we know that addr will be in the range 0..31 and thus the
* implicit cast to a signed int is not a problem.
*/
return addr;
}
And call u8 addr = phy_package_address(phydev, addr_offset);
Maybe one if can be skipped with the following fun thing?
static int phy_package_address(struct phy_device *phydev,
unsigned int addr_offset)
{
struct phy_package_shared *shared = phydev->shared;
u8 base_addr = shared->base_addr;
if (addr_offset >= PHY_MAX_ADDR - base_addr)
return -EIO;
/* we know that addr will be in the range 0..31 and thus the
* implicit cast to a signed int is not a problem.
*/
return base_addr + addr_offset;
}
(don't hate me it's late here and my brain is half working ahahha)
>
> Honestly, I have wondered why the mdio bus address is a signed int, but
> never decided to do anything about it.
>
Maybe because direct usage of mdiobus_ is discouraged and phy_write will
use an addr that is already validated.
--
Ansuel
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