linux-kernel - Re: [PATCH net-next v4] ethernet: fix PTP_1588

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Date:   Thu, 5 Aug 2021 22:52:41 +1000
From:   Julian Calaby <julian.calaby@...il.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Richard Cochran <richardcochran@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Shannon Nelson <snelson@...sando.io>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        drivers@...sando.io, Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Yangbo Lu <yangbo.lu@....com>, Karen Xie <kxie@...lsio.com>,
        netdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        linux-rdma@...r.kernel.org,
        Linux SCSI List <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH net-next v4] ethernet: fix PTP_1588_CLOCK dependencies

Hi Arnd,

On Thu, Aug 5, 2021 at 9:49 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> The 'imply' keyword does not do what most people think it does, it only
> politely asks Kconfig to turn on another symbol, but does not prevent
> it from being disabled manually or built as a loadable module when the
> user is built-in. In the ICE driver, the latter now causes a link failure:
>
> aarch64-linux-ld: drivers/net/ethernet/intel/ice/ice_main.o: in function `ice_eth_ioctl':
> ice_main.c:(.text+0x13b0): undefined reference to `ice_ptp_get_ts_config'
> ice_main.c:(.text+0x13b0): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `ice_ptp_get_ts_config'
> aarch64-linux-ld: ice_main.c:(.text+0x13bc): undefined reference to `ice_ptp_set_ts_config'
> ice_main.c:(.text+0x13bc): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `ice_ptp_set_ts_config'
> aarch64-linux-ld: drivers/net/ethernet/intel/ice/ice_main.o: in function `ice_prepare_for_reset':
> ice_main.c:(.text+0x31fc): undefined reference to `ice_ptp_release'
> ice_main.c:(.text+0x31fc): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `ice_ptp_release'
> aarch64-linux-ld: drivers/net/ethernet/intel/ice/ice_main.o: in function `ice_rebuild':
>
> This is a recurring problem in many drivers, and we have discussed
> it several times befores, without reaching a consensus. I'm providing
> a link to the previous email thread for reference, which discusses
> some related problems.
>
> To solve the dependency issue better than the 'imply' keyword, introduce a
> separate Kconfig symbol "CONFIG_PTP_1588_CLOCK_OPTIONAL" that any driver
> can depend on if it is able to use PTP support when available, but works
> fine without it. Whenever CONFIG_PTP_1588_CLOCK=m, those drivers are
> then prevented from being built-in, the same way as with a 'depends on
> PTP_1588_CLOCK || !PTP_1588_CLOCK' dependency that does the same trick,
> but that can be rather confusing when you first see it.
>
> Since this should cover the dependencies correctly, the IS_REACHABLE()
> hack in the header is no longer needed now, and can be turned back
> into a normal IS_ENABLED() check. Any driver that gets the dependency
> wrong will now cause a link time failure rather than being unable to use
> PTP support when that is in a loadable module.
>
> However, the two recently added ptp_get_vclocks_index() and
> ptp_convert_timestamp() interfaces are only called from builtin code with
> ethtool and socket timestamps, so keep the current behavior by stubbing
> those out completely when PTP is in a loadable module. This should be
> addressed properly in a follow-up.
>
> As Richard suggested, we may want to actually turn PTP support into a
> 'bool' option later on, preventing it from being a loadable module
> altogether, which would be one way to solve the problem with the ethtool
> interface.
>
> Fixes: 06c16d89d2cb ("ice: register 1588 PTP clock device object for E810 devices")
> Link: https://lore.kernel.org/netdev/20210804121318.337276-1-arnd@kernel.org/
> Link: https://lore.kernel.org/netdev/CAK8P3a06enZOf=XyZ+zcAwBczv41UuCTz+=0FMf2gBz1_cOnZQ@mail.gmail.com/
> Link: https://lore.kernel.org/netdev/CAK8P3a3=eOxE-K25754+fB_-i_0BZzf9a9RfPTX3ppSwu9WZXw@mail.gmail.com/
> Link: https://lore.kernel.org/netdev/20210726084540.3282344-1-arnd@kernel.org/
> Acked-by: Shannon Nelson <snelson@...sando.io>
> Acked-by: Jacob Keller <jacob.e.keller@...el.com>
> Acked-by: Richard Cochran <richardcochran@...il.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

> diff --git a/drivers/scsi/cxgbi/cxgb4i/Kconfig b/drivers/scsi/cxgbi/cxgb4i/Kconfig
> index 8b0deece9758..e78c07f08cdf 100644
> --- a/drivers/scsi/cxgbi/cxgb4i/Kconfig
> +++ b/drivers/scsi/cxgbi/cxgb4i/Kconfig
> @@ -2,6 +2,7 @@
>  config SCSI_CXGB4_ISCSI
>         tristate "Chelsio T4 iSCSI support"
>         depends on PCI && INET && (IPV6 || IPV6=n)
> ++      depends on PTP_1588_CLOCK_OPTIONAL

Extra +?

Thanks,

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/