From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Danielle Ratson <danieller@nvidia.com>
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, corbet@lwn.net,
sdf@google.com, kory.maincent@bootlin.com,
maxime.chevallier@bootlin.com, vladimir.oltean@nxp.com,
przemyslaw.kitszel@intel.com, ahmed.zaki@intel.com,
richardcochran@gmail.com, shayagr@amazon.com,
paul.greenwalt@intel.com, jiri@resnulli.us,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
mlxsw@nvidia.com, petrm@nvidia.com, idosch@nvidia.com
Subject: Re: [RFC PATCH net-next 7/9] ethtool: cmis_cdb: Add a layer for supporting CDB commands
Date: Tue, 23 Jan 2024 17:17:46 +0000 [thread overview]
Message-ID: <Za/0um6oUo3CQaR2@shell.armlinux.org.uk> (raw)
In-Reply-To: <20240122084530.32451-8-danieller@nvidia.com>
On Mon, Jan 22, 2024 at 10:45:28AM +0200, Danielle Ratson wrote:
> +int ethtool_cmis_page_init(struct ethtool_module_eeprom *page_data,
> + u8 page, u32 offset, u32 length)
> +{
> + page_data->page = page;
> + page_data->offset = offset;
> + page_data->length = length;
> + page_data->i2c_address = ETHTOOL_CMIS_CDB_PAGE_I2C_ADDR;
> + page_data->data = kmalloc(page_data->length, GFP_KERNEL);
> + if (!page_data->data)
> + return -ENOMEM;
Hmm, so every use is forced to use kmalloc() even when it's just one
byte? That seems rather wasteful.
> +/* See section 9.4.1 "CMD 0040h: Module Features" in CMIS standard revision 5.2.
> + * struct cmis_cdb_module_features_rpl is structured layout of the flat
> + * array, ethtool_cmis_cdb_rpl::payload.
> + */
> +struct cmis_cdb_module_features_rpl {
> + u8 resv1[CMIS_CDB_MODULE_FEATURES_RESV_DATA];
> + __be16 max_completion_time;
> +};
Does this structure need to be packed? I would suggest it does to
ensure that the __be16 is correctly placed after the 34 bytes of u8.
Overall, I think the idea of always kmalloc()ing the data is a bad idea
at the moment. We have no implementations that DMA to/from this buffer,
and it means extra cycles spent, and an extra failure point each time
we want to do a CMIS command.
It also introduces extra complexity, where we could just be passing
a pointer to a function local variable or function local structure.
Unless we decide that the data pointer should be DMA-able from (in
which case, that needs documenting as such) then I would suggest
getting rid of the extra kmalloc()...kfree() bits.
Thanks.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
next prev parent reply other threads:[~2024-01-23 17:17 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-22 8:45 [RFC PATCH net-next 0/9] Add ability to flash modules' firmware Danielle Ratson
2024-01-22 8:45 ` [RFC PATCH net-next 1/9] ethtool: Add ethtool operation to write to a transceiver module EEPROM Danielle Ratson
2024-01-23 17:03 ` Russell King (Oracle)
2024-01-24 13:10 ` Danielle Ratson
2024-01-25 20:26 ` Andrew Lunn
2024-01-25 20:45 ` Andrew Lunn
2024-01-30 7:43 ` Danielle Ratson
2024-01-31 11:51 ` Danielle Ratson
2024-01-22 8:45 ` [RFC PATCH net-next 2/9] mlxsw: Implement " Danielle Ratson
2024-01-22 8:45 ` [RFC PATCH net-next 3/9] ethtool: Add an interface for flashing transceiver modules' firmware Danielle Ratson
2024-01-23 1:37 ` Jakub Kicinski
2024-01-23 4:50 ` Jakub Kicinski
2024-01-23 13:34 ` Danielle Ratson
2024-01-23 15:53 ` Jakub Kicinski
2024-01-22 8:45 ` [RFC PATCH net-next 4/9] ethtool: Add flashing transceiver modules' firmware notifications ability Danielle Ratson
2024-01-22 8:45 ` [RFC PATCH net-next 5/9] include: netdevice: Add module firmware flashing in progress flag to net_device Danielle Ratson
2024-01-22 8:45 ` [RFC PATCH net-next 6/9] net: sfp: Add more extended compliance codes Danielle Ratson
2024-01-23 17:09 ` Russell King (Oracle)
2024-01-22 8:45 ` [RFC PATCH net-next 7/9] ethtool: cmis_cdb: Add a layer for supporting CDB commands Danielle Ratson
2024-01-22 10:31 ` Simon Horman
2024-01-22 14:35 ` Danielle Ratson
2024-01-22 20:03 ` Simon Horman
2024-01-23 17:17 ` Russell King (Oracle) [this message]
2024-01-30 7:55 ` Danielle Ratson
2024-01-22 8:45 ` [RFC PATCH net-next 8/9] ethtool: cmis_fw_update: add a layer for supporting firmware update using CDB Danielle Ratson
2024-01-23 4:44 ` Jakub Kicinski
2024-01-23 12:08 ` Danielle Ratson
2024-01-23 5:07 ` Jakub Kicinski
2024-01-22 8:45 ` [RFC PATCH net-next 9/9] ethtool: Add ability to flash transceiver modules' firmware Danielle Ratson
2024-01-22 10:37 ` Simon Horman
2024-01-22 15:25 ` Danielle Ratson
2024-01-23 5:05 ` Jakub Kicinski
2024-01-23 13:05 ` Danielle Ratson
2024-01-23 15:49 ` Jakub Kicinski
2024-01-24 15:46 ` Danielle Ratson
2024-01-24 17:06 ` Jakub Kicinski
2024-01-23 16:27 ` Russell King (Oracle)
2024-01-24 13:11 ` Danielle Ratson
2024-01-25 21:03 ` Andrew Lunn
2024-01-31 15:48 ` Danielle Ratson
2024-01-31 15:52 ` Danielle Ratson
2024-01-31 16:30 ` Andrew Lunn
2024-04-08 12:50 ` Danielle Ratson
2024-04-08 23:53 ` Andrew Lunn
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