linux-kernel - Re: [PATCH arm/aspeed/ast2500 v2] ipmi: add an Aspeed KCS IPMI BMC driver

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Message-ID: <793dbcc0-4d28-cddb-c5eb-bf491dff4d92@linux.intel.com>
Date:   Fri, 26 Jan 2018 13:33:22 +0800
From:   "Wang, Haiyue" <haiyue.wang@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        minyard@....org, joel@....id.au, avifishman70@...il.com,
        openbmc@...ts.ozlabs.org, openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH arm/aspeed/ast2500 v2] ipmi: add an Aspeed KCS IPMI BMC
 driver



On 2018-01-25 01:05, Andy Shevchenko wrote:
> On Thu, 2018-01-25 at 00:06 +0800, Haiyue Wang wrote:
>> The KCS (Keyboard Controller Style) interface is used to perform in-
>> band
>> IPMI communication between a server host and its BMC (BaseBoard
>> Management
>> Controllers).
>>
>>
>> +config ASPEED_KCS_IPMI_BMC
>> +	depends on ARCH_ASPEED || COMPILE_TEST
>> +	depends on IPMI_KCS_BMC
>> +	select REGMAP_MMIO
>> +	tristate "Aspeed KCS IPMI BMC driver"
>> +	help
>> +	  Provides a driver for the KCS (Keyboard Controller Style)
>> IPMI
>> +	  interface found on Aspeed SOCs (AST2400 and AST2500).
>> +
>> +	  The driver implements the BMC side of the KCS contorller,
>> it
>> +	  provides the access of KCS IO space for BMC side.
>> +static inline u8 read_data(struct kcs_bmc *kcs_bmc)
>> +{
>> +	return kcs_bmc->io_inputb(kcs_bmc, kcs_bmc->ioreg.idr);
>> +}
>> +
>> +static inline void write_data(struct kcs_bmc *kcs_bmc, u8 data)
>> +{
>> +	kcs_bmc->io_outputb(kcs_bmc, kcs_bmc->ioreg.odr, data);
>> +}
>> +
>> +static inline u8 read_status(struct kcs_bmc *kcs_bmc)
>> +{
>> +	return kcs_bmc->io_inputb(kcs_bmc, kcs_bmc->ioreg.str);
>> +}
>> +
>> +static inline void write_status(struct kcs_bmc *kcs_bmc, u8 data)
>> +{
>> +	kcs_bmc->io_outputb(kcs_bmc, kcs_bmc->ioreg.str, data);
>> +}
>> +
>> +static void update_status_bits(struct kcs_bmc *kcs_bmc, u8 mask, u8
>> val)
>> +{
>> +	u8 tmp;
>> +
>> +	tmp = read_status(kcs_bmc);
>> +
>> +	tmp &= ~mask;
>> +	tmp |= val & mask;
>> +
>> +	write_status(kcs_bmc, tmp);
>> +}
> Shouldn't be above some kind of regmap API?
It is KCS spec defined IO access for hidden the low level, if the low 
level supports regmap, such as in kcs_bmc_aspeed.c,
aspeed_kcs_inb & aspeed_kcs_outb.
>
>> +/* Different phases of the KCS BMC module */
>> +enum kcs_phases {
>> +	/* BMC should not be expecting nor sending any data. */
>> +	KCS_PHASE_IDLE,
> Perhaps kernel-doc?
Code + inline comments should be better than kernel-doc ? Or move it out 
like :

/* The interface for checksum offload between the stack and networking 
drivers
  * is as follows...
  *
  * A. IP checksum related features
  *
  * Drivers advertise checksum offload capabilities in the features of a 
device.
  * From the stack's point of view these are capabilities offered by the 
driver,
  * a driver typically only advertises features that it is capable of 
offloading
  * to its device.
  *
  * The checksum related features are:
  *
  *    NETIF_F_HW_CSUM    - The driver (or its device) is able to 
compute one
  *              IP (one's complement) checksum for any combination
  *              of protocols or protocol layering. The checksum is
  *              computed and set in a packet per the CHECKSUM_PARTIAL
  *              interface (see below).
  *
  *    NETIF_F_IP_CSUM - Driver (device) is only able to checksum plain
  *              TCP or UDP packets over IPv4. These are specifically
  *              unencapsulated packets of the form IPv4|TCP or
  *              IPv4|UDP where the Protocol field in the IPv4 header
  *              is TCP or UDP. The IPv4 header may contain IP options
  *              This feature cannot be set in features for a device
  *              with NETIF_F_HW_CSUM also set. This feature is being
  *              DEPRECATED (see below).
>> +};
>
>> +/* IPMI 2.0 - 9.5, KCS Interface Registers */
>> +struct kcs_ioreg {
>> +	u32 idr; /* Input Data Register */
>> +	u32 odr; /* Output Data Register */
>> +	u32 str; /* Status Register */
> kernel-doc
>> +};
>> +
>> +static inline void *kcs_bmc_priv(const struct kcs_bmc *kcs_bmc)
>> +{
>> +	return kcs_bmc->priv;
>> +}
>> +
>> +extern int kcs_bmc_handle_event(struct kcs_bmc *kcs_bmc);
>> +extern struct kcs_bmc *kcs_bmc_alloc(struct device *dev, int
>> sizeof_priv,
>> +					u32 channel);
> Drop extern.
After dropping extern, it truly passed compilation, have any special 
reason to drop 'extern' ?
I saw in kernel still use extern like : extern void printk_nmi_init(void);
>> +#endif
> Next one could be reviewed when you split this patch to two.
Got it!