linux-kernel - Re: [PATCH v8 1/3] ipmi: ssif

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Message-ID: <7b9923c0-50f0-556a-657c-9cf0ef9af5aa@wanadoo.fr>
Date:   Thu, 16 Jun 2022 22:47:39 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     quan@...amperecomputing.com
Cc:     andrew@...id.au, benh@...nel.crashing.org,
        brendanhiggins@...gle.com, devicetree@...r.kernel.org,
        joel@....id.au, krzysztof.kozlowski+dt@...aro.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, minyard@....org,
        openbmc@...ts.ozlabs.org, openipmi-developer@...ts.sourceforge.net,
        patches@...erecomputing.com, phong@...amperecomputing.com,
        robh+dt@...nel.org, thang@...amperecomputing.com, wsa@...nel.org
Subject: Re: [PATCH v8 1/3] ipmi: ssif_bmc: Add SSIF BMC driver

Le 15/06/2022 à 11:02, Quan Nguyen a écrit :
> The SMBus system interface (SSIF) IPMI BMC driver can be used to perform
> in-band IPMI communication with their host in management (BMC) side.
> 
> Thanks Dan for the copy_from_user() fix in the link below.
> 
> Link: https://lore.kernel.org/linux-arm-kernel/20220310114119.13736-4-quan-shex6MNQR2J/SfDzf78azzKzEDxYleXD@public.gmane.org/
> Signed-off-by: Quan Nguyen <quan-shex6MNQR2J/SfDzf78azzKzEDxYleXD@...lic.gmane.org>
> ---

Hi,

a few nitpick below

[...]

> diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
> new file mode 100644
> index 000000000000..0bfd4b9bbaf1
> --- /dev/null
> +++ b/drivers/char/ipmi/ssif_bmc.c
> @@ -0,0 +1,880 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * The driver for BMC side of SSIF interface
> + *
> + * Copyright (c) 2022, Ampere Computing LLC
> + *
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/miscdevice.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/poll.h>
> +#include <linux/sched.h>
> +#include <linux/mutex.h>
> +#include <linux/spinlock.h>
> +#include <linux/timer.h>
> +#include <linux/jiffies.h>
> +#include <linux/ipmi_ssif_bmc.h>
> +
> +#define DEVICE_NAME                             "ipmi-ssif-host"
> +
> +#define GET_8BIT_ADDR(addr_7bit)                (((addr_7bit) << 1) & 0xff)
> +
> +/* A standard SMBus Transaction is limited to 32 data bytes */
> +#define MAX_PAYLOAD_PER_TRANSACTION             32
> +/* Transaction includes the address, the command, the length and the PEC byte */
> +#define MAX_TRANSACTION                         (MAX_PAYLOAD_PER_TRANSACTION + 4)
> +
> +#define MAX_IPMI_DATA_PER_START_TRANSACTION     30
> +#define MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION    31
> +
> +#define SSIF_IPMI_SINGLEPART_WRITE              0x2
> +#define SSIF_IPMI_SINGLEPART_READ               0x3
> +#define SSIF_IPMI_MULTIPART_WRITE_START         0x6
> +#define SSIF_IPMI_MULTIPART_WRITE_MIDDLE        0x7
> +#define SSIF_IPMI_MULTIPART_WRITE_END           0x8
> +#define SSIF_IPMI_MULTIPART_READ_START          0x3
> +#define SSIF_IPMI_MULTIPART_READ_MIDDLE         0x9
> +
> +/*
> + * IPMI 2.0 Spec, section 12.7 SSIF Timing,
> + * Request-to-Response Time is T6max(250ms) - T1max(20ms) - 3ms = 227ms
> + * Recover ssif_bmc from busy state if it takes up to 500ms
> + */
> +#define RESPONSE_TIMEOUT                        500 /* ms */
> +
> +struct ssif_part_buffer {
> +	u8 address;
> +	u8 smbus_cmd;
> +	u8 length;
> +	u8 payload[MAX_PAYLOAD_PER_TRANSACTION];
> +	u8 pec;
> +	u8 index;
> +};
> +
> +/*
> + * SSIF internal states:
> + *   SSIF_READY         0x00 : Ready state
> + *   SSIF_START         0x01 : Start smbus transaction
> + *   SSIF_SMBUS_CMD     0x02 : Received SMBus command
> + *   SSIF_REQ_RECVING   0x03 : Receiving request
> + *   SSIF_RES_SENDING   0x04 : Sending response
> + *   SSIF_BAD_SMBUS     0x05 : Bad SMbus transaction

If these states are related to the enum just below, 
s/SSIF_BAD_SMBUS/SSIF_ABORTING/ + description update?

> + */
> +enum ssif_state {
> +	SSIF_READY,
> +	SSIF_START,
> +	SSIF_SMBUS_CMD,
> +	SSIF_REQ_RECVING,
> +	SSIF_RES_SENDING,
> +	SSIF_ABORTING,
> +	SSIF_STATE_MAX
> +};
> +

[...]

> +static int ssif_bmc_probe(struct i2c_client *client, const struct i2c_device_id *id)
> +{
> +	struct ssif_bmc_ctx *ssif_bmc;
> +	int ret;
> +
> +	ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc), GFP_KERNEL);
> +	if (!ssif_bmc)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&ssif_bmc->lock);
> +
> +	init_waitqueue_head(&ssif_bmc->wait_queue);
> +	ssif_bmc->request_available = false;
> +	ssif_bmc->response_in_progress = false;
> +	ssif_bmc->busy = false;
> +	ssif_bmc->response_timer_inited = false;
> +
> +	/* Register misc device interface */
> +	ssif_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
> +	ssif_bmc->miscdev.name = DEVICE_NAME;
> +	ssif_bmc->miscdev.fops = &ssif_bmc_fops;
> +	ssif_bmc->miscdev.parent = &client->dev;
> +	ret = misc_register(&ssif_bmc->miscdev);
> +	if (ret)
> +		goto out;

Could be "return ret;"
(see below)

> +
> +	ssif_bmc->client = client;
> +	ssif_bmc->client->flags |= I2C_CLIENT_SLAVE;
> +
> +	/* Register I2C slave */
> +	i2c_set_clientdata(client, ssif_bmc);
> +	ret = i2c_slave_register(client, ssif_bmc_cb);
> +	if (ret) {
> +		misc_deregister(&ssif_bmc->miscdev);
> +		goto out;
> +	}
> +
> +	return 0;
> +out:
> +	devm_kfree(&client->dev, ssif_bmc);

This looks useless to me. The whole error handling path could be 
removed, or updated to only have the "misc_deregister()" above.

CJ

> +	return ret;
> +}