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[2a01:c22:7af7:5300:8868:b389:215f:d1]) by smtp.googlemail.com with ESMTPSA id f24-20020a1c6a18000000b003b95ed78275sm6355101wmc.20.2022.12.17.09.22.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 17 Dec 2022 09:22:01 -0800 (PST) Message-ID: Date: Sat, 17 Dec 2022 18:07:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 From: Heiner Kallweit Subject: Re: [PATCH 6/8] i2c: i801: add i801_single_transaction(), complementing i801_block_transaction() To: Jean Delvare Cc: linux-i2c@vger.kernel.org References: <4125f9ce-ce5f-fbcf-7d6f-9bc586ac43e0@gmail.com> <20220610130324.1ab2725d@endymion.delvare> Content-Language: en-US In-Reply-To: <20220610130324.1ab2725d@endymion.delvare> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On 10.06.2022 13:03, Jean Delvare wrote: > Hi Heiner, > > On Fri, 15 Apr 2022 18:58:03 +0200, Heiner Kallweit wrote: >> This patch factors out non-block pre/post processing to a new function >> i801_single_transaction(), complementing existing function >> i801_block_transaction(). This makes i801_access() better readable. > > I like the idea, but I have objections about some implementation > details, see below. > >> Signed-off-by: Heiner Kallweit >> --- >> drivers/i2c/busses/i2c-i801.c | 95 +++++++++++++++++++++-------------- >> 1 file changed, 58 insertions(+), 37 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c >> index bf77f8640..8c2245f38 100644 >> --- a/drivers/i2c/busses/i2c-i801.c >> +++ b/drivers/i2c/busses/i2c-i801.c >> @@ -771,6 +771,62 @@ static int i801_block_transaction(struct i801_priv *priv, union i2c_smbus_data * >> return result; >> } >> >> +/* Single transaction function */ > > The term "single transaction" is a bit misleading. Block transactions > are also single transactions, in the sense that there's one start > condition at the beginning and one stop condition at the end. I'd > rather call non-block transactions "single value transactions" or > "simple transactions". > OK >> +static int i801_single_transaction(struct i801_priv *priv, union i2c_smbus_data *data, >> + char read_write, int command) >> +{ >> + int xact, ret; >> + >> + switch (command) { >> + case I2C_SMBUS_QUICK: >> + xact = I801_QUICK; >> + break; >> + case I2C_SMBUS_BYTE: >> + xact = I801_BYTE; >> + break; > > Previous 2 lines are indented with spaces instead of tabs. > OK >> + case I2C_SMBUS_BYTE_DATA: >> + if (read_write == I2C_SMBUS_WRITE) >> + outb_p(data->byte, SMBHSTDAT0(priv)); >> + xact = I801_BYTE_DATA; >> + break; >> + case I2C_SMBUS_WORD_DATA: >> + if (read_write == I2C_SMBUS_WRITE) { >> + outb_p(data->word & 0xff, SMBHSTDAT0(priv)); >> + outb_p((data->word & 0xff00) >> 8, SMBHSTDAT1(priv)); >> + } >> + xact = I801_WORD_DATA; >> + break; >> + case I2C_SMBUS_PROC_CALL: >> + outb_p(data->word & 0xff, SMBHSTDAT0(priv)); >> + outb_p((data->word & 0xff00) >> 8, SMBHSTDAT1(priv)); >> + xact = I801_PROC_CALL; >> + break; >> + default: >> + return -EOPNOTSUPP; > > That's never going to happen. > > Generally speaking, I'm worried about having the same switch/case > construct here that we already have in i801_access. Looks to me like we > are doing half of the work here and the other half there and I fail to > see the rationale for splitting the work like that. I mean, I see how > it solves the asymmetry between the block and non-block code paths, but > the result doesn't look appealing. From a performance perspective it's > questionable too. > > What prevents us from doing all the work on either side? Maybe we > should move more code into i801_single_transaction (possibly in a > subsequent patch)? > Makes sense. Ill add this in v2. >> + } >> + >> + ret = i801_transaction(priv, xact); >> + > > Traditionally no blank line here. > OK >> + if (ret || read_write == I2C_SMBUS_WRITE) >> + return ret; >> + >> + switch (command) { >> + case I2C_SMBUS_BYTE: >> + case I2C_SMBUS_BYTE_DATA: >> + data->byte = inb_p(SMBHSTDAT0(priv)); >> + break; >> + case I2C_SMBUS_WORD_DATA: >> + case I2C_SMBUS_PROC_CALL: >> + data->word = inb_p(SMBHSTDAT0(priv)) + >> + (inb_p(SMBHSTDAT1(priv)) << 8); >> + break; >> + default: >> + break; > > Default case is not needed. > OK >> + } >> + >> + return 0; >> +} >> + >> static void i801_set_hstadd(struct i801_priv *priv, u8 addr, char read_write) >> { >> addr <<= 1; >> @@ -784,9 +840,7 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr, >> unsigned short flags, char read_write, u8 command, >> int size, union i2c_smbus_data *data) >> { >> - int hwpec; >> - int block = 0; >> - int ret, xact; >> + int hwpec, ret, block = 0; >> struct i801_priv *priv = i2c_get_adapdata(adap); >> >> mutex_lock(&priv->acpi_lock); >> @@ -804,36 +858,23 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr, >> switch (size) { >> case I2C_SMBUS_QUICK: >> i801_set_hstadd(priv, addr, read_write); >> - xact = I801_QUICK; >> break; >> case I2C_SMBUS_BYTE: >> i801_set_hstadd(priv, addr, read_write); >> if (read_write == I2C_SMBUS_WRITE) >> outb_p(command, SMBHSTCMD(priv)); >> - xact = I801_BYTE; >> break; >> case I2C_SMBUS_BYTE_DATA: >> i801_set_hstadd(priv, addr, read_write); >> outb_p(command, SMBHSTCMD(priv)); >> - if (read_write == I2C_SMBUS_WRITE) >> - outb_p(data->byte, SMBHSTDAT0(priv)); >> - xact = I801_BYTE_DATA; >> break; >> case I2C_SMBUS_WORD_DATA: >> i801_set_hstadd(priv, addr, read_write); >> outb_p(command, SMBHSTCMD(priv)); >> - if (read_write == I2C_SMBUS_WRITE) { >> - outb_p(data->word & 0xff, SMBHSTDAT0(priv)); >> - outb_p((data->word & 0xff00) >> 8, SMBHSTDAT1(priv)); >> - } >> - xact = I801_WORD_DATA; >> break; >> case I2C_SMBUS_PROC_CALL: >> i801_set_hstadd(priv, addr, I2C_SMBUS_WRITE); >> outb_p(command, SMBHSTCMD(priv)); >> - outb_p(data->word & 0xff, SMBHSTDAT0(priv)); >> - outb_p((data->word & 0xff00) >> 8, SMBHSTDAT1(priv)); >> - xact = I801_PROC_CALL; >> read_write = I2C_SMBUS_READ; >> break; >> case I2C_SMBUS_BLOCK_DATA: >> @@ -883,7 +924,7 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr, >> if (block) >> ret = i801_block_transaction(priv, data, read_write, size); >> else >> - ret = i801_transaction(priv, xact); >> + ret = i801_single_transaction(priv, data, read_write, size); >> >> /* Some BIOSes don't like it when PEC is enabled at reboot or resume >> time, so we forcibly disable it after every transaction. Turn off >> @@ -891,26 +932,6 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr, >> if (hwpec || block) >> outb_p(inb_p(SMBAUXCTL(priv)) & >> ~(SMBAUXCTL_CRC | SMBAUXCTL_E32B), SMBAUXCTL(priv)); >> - >> - if (block) >> - goto out; >> - if (ret) >> - goto out; >> - if ((read_write == I2C_SMBUS_WRITE) || (xact == I801_QUICK)) >> - goto out; >> - >> - switch (xact) { >> - case I801_BYTE: /* Result put in SMBHSTDAT0 */ >> - case I801_BYTE_DATA: >> - data->byte = inb_p(SMBHSTDAT0(priv)); >> - break; >> - case I801_WORD_DATA: >> - case I801_PROC_CALL: >> - data->word = inb_p(SMBHSTDAT0(priv)) + >> - (inb_p(SMBHSTDAT1(priv)) << 8); >> - break; >> - } >> - >> out: >> /* >> * Unlock the SMBus device for use by BIOS/ACPI, > >