Re: [PATCH net-next v2 2/3] bnxt_en: add .get_module_eeprom_by_page() support

From: Vikas Gupta <vikas.gupta@broadcom.com>
To: Ido Schimmel <idosch@idosch.org>
Cc: Michael Chan <michael.chan@broadcom.com>,
	davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org,
	edumazet@google.com, pabeni@redhat.com, gospo@broadcom.com
Subject: Re: [PATCH net-next v2 2/3] bnxt_en: add .get_module_eeprom_by_page() support
Date: Sun, 2 Oct 2022 21:51:10 +0530	[thread overview]
Message-ID: <CAHLZf_sEB=dR2skpVuTD-r=SW4ZF9aOUKuNxibrjAKFe=v5+=Q@mail.gmail.com> (raw)
In-Reply-To: <YzmvdxQpWviawxuj@shredder>

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Hi Ido,

On Sun, Oct 2, 2022 at 9:04 PM Ido Schimmel <idosch@idosch.org> wrote:
>
> On Sat, Oct 01, 2022 at 02:27:10PM -0400, Michael Chan wrote:
> > +static int bnxt_get_module_eeprom_by_page(struct net_device *dev,
> > +                                       const struct ethtool_module_eeprom *page_data,
> > +                                       struct netlink_ext_ack *extack)
> > +{
> > +     struct bnxt *bp = netdev_priv(dev);
> > +     int rc;
> > +
> > +     if (bp->link_info.module_status >
> > +         PORT_PHY_QCFG_RESP_MODULE_STATUS_WARNINGMSG) {
> > +             NL_SET_ERR_MSG_MOD(extack, "Phy status unknown");
>
> Can you make this more helpful to users? The comment above this check in
> bnxt_get_module_info() suggests that it is possible:

Do you mean that we should elaborate something like
NL_SET_ERR_MSG_MOD(extack, "Module may be not inserted or powered down
or 10G Base-T");

>
> /* No point in going further if phy status indicates
>  * module is not inserted or if it is powered down or
>  * if it is of type 10GBase-T
>  */
> if (bp->link_info.module_status >
>         PORT_PHY_QCFG_RESP_MODULE_STATUS_WARNINGMSG)
>
> > +             return -EIO;
> > +     }
> > +
> > +     if (bp->hwrm_spec_code < 0x10202) {
> > +             NL_SET_ERR_MSG_MOD(extack, "Unsupported hwrm spec");
>
> Likewise. As a user I do not know what "hwrm spec" means... Maybe:
>
> NL_SET_ERR_MSG_MOD(extack, "Firmware version too old");
>
>
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> > +     if (page_data->bank && !(bp->phy_flags & BNXT_PHY_FL_BANK_SEL)) {
> > +             NL_SET_ERR_MSG_MOD(extack, "Firmware not capable for bank selection");
> > +             return -EOPNOTSUPP;
>
> What happens if you have an old firmware that does not support this
> functionality and user space tries to dump page 10h from bank 1 of a
> CMIS module that supports multiple banks?
>
> I wanted to say that you would see the wrong information (from bank 0)
> because the legacy operations do not support banks and bank 0 is
> assumed. However, because only pages 10h-ffh are banked, user space will
> get an error from the following check in fallback_set_params():
>
> if (request->page)
>         offset = request->page * ETH_MODULE_EEPROM_PAGE_LEN + offset;
>
> [...]
>
> if (offset >= modinfo->eeprom_len)
>         return -EINVAL;
>
> I believe it makes sense to be more explicit about it and return an
> error in fallback_set_params() in case bank is not 0. Please follow up
> if the above analysis is correct.

So older firmware do not understand bank > 0 and hence it returns to
EOPNOTSUPP, which goes to fallback_set_params() and fails for
if (offset >= modinfo->eeprom_len)
        return -EINVAL
As we are not setting modinfo->eeprom_len for CMIS modules in get_module_eeprom.
With the above said userspace gets EINVAL.
Let me know if my understanding is correct?

Thanks,
Vikas

>
> > +     }
> > +
> > +     rc = bnxt_read_sfp_module_eeprom_info(bp, page_data->i2c_address << 1,
>
> I was wondering why the shift is needed, but I see that in other places
> you are passing 0xA0 and 0xA2 instead of 0x50 and 0x51, so it is OK.
>
> > +                                           page_data->page, page_data->bank,
> > +                                           page_data->offset,
> > +                                           page_data->length,
> > +                                           page_data->data);
> > +     if (rc) {
> > +             NL_SET_ERR_MSG_MOD(extack, "Module`s eeprom read failed");
> > +             return rc;
> > +     }
> > +     return page_data->length;
> > +}
>
> Looks good otherwise.
>
> Thanks

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